Negative photosensitive lithograhic printing plate

ABSTRACT

A negative photosensitive lithographic printing plate comprises: a support; and a photosensitive layer containing: i) a modified poly(vinyl alcohol) resin binder having a radical-polymerizable group and an acid group; and ii) at least one of a photo-polymerization initiator and a heat-polymerization initiator.

FIELD OF THE INVENTION

The present invention relates to a negative photosensitive lithographicprinting plate. More particularly, the invention relates to a negativephotosensitive lithographic printing plate suitable for drawing with alaser beam.

BACKGROUND OF THE INVENTION

PS plates comprising a hydrophilic support and an oleophilicphotosensitive resin layer formed thereon have hitherto been widely usedas negative photosensitive lithographic printing plates. In general, adesired printing plate has been obtained from the PS plate by subjectingit to exposure to light (a real exposure) through a mask, i.e., a lithfilm, and then removing the nonimage areas by dissolution.

In recent years, the digitization technology in which image informationis electronically processed, stored, and outputted with a computer isspreading widely. With this trend, various new techniques for imageoutput which are suitable for the digitization technology have come tobe practically used. As a result, it is desired to establish acomputer-to-plate (CTP) technology in which a photosensitive resin layeris scanned with a highly directional light such as a laser beamaccording to digitized image information to thereby directly produce aprinting plate without via the use of a lith film. An importanttechnical subject therefore is to obtain a negative photosensitivelithographic printing plate suitable for use in that technology.

A negative photosensitive lithographic printing plate capable of suchscanning exposure has been proposed which comprises a hydrophilicsupport and formed thereon an oleophilic photosensitive resin layer(hereinafter referred to also as “photosensitive layer”) containing aphotosensitive compound capable of generating an active species such asradicals or a Brφnstead acid, upon exposure to a laser beam. Thenegative photosensitive lithographic printing plate has already been puton the market. From this negative photosensitive lithographic printingplate can be obtained a negative lithographic printing plate by scanningit with a laser beam based on digital information to generate an activespecies, causing the photosensitive layer to undergo a physical orchemical change by the action of the active species to therebyinsolubilize the exposed areas of the layer, and subsequently developingthe layer.

In particular, a negative photosensitive lithographic printing platewhich comprises a hydrophilic support and formed thereon aphotopolymerization type photosensitive layer having a highphotosensitization speed containing a photopolymerization initiator, anethylenically unsaturated compound capable of undergoing additionpolymerization, and a polymeric binder soluble in an alkaline developingsolution and which optionally has a protective layer having oxygenbarrier properties, attains excellent productivity, can be developedeasily, and can give a printing plate having desirable printingperformances because of its advantages of high resolution andsatisfactory ink receptivity.

Organic polymers developable with an alkali have hitherto been used asthe polymeric binders serving as components of photosensitive layers.Examples thereof include the methacrylic acid copolymers, acrylic acidcopolymers, itaconic acid copolymers, crotonic acid copolymers, maleicacid copolymers, and partially esterified maleic acid copolymers shownin, e.g., Japanese Patent Laid-Open No. 44615/1984, Japanese PatentPublication Nos. 34327/1979, 12577/1983, and 25957/1979, and JapanesePatent Laid-Open Nos. 92723/1979, 53836/1984, and 71048/1984.

However, the negative photosensitive lithographic printing plates havinga photosensitive layer containing such a conventional polymeric binderhave had the following problem. When the speed of scanning is increasedin order to further heighten productivity, the exposed areas come not tobe sufficiently cured because the exposure light energy applied theretoper unit area becomes lower accordingly. As a result, the image areasare damaged during development by the alkali ingredient contained in thedeveloping solution, so that high press life cannot be obtained.Consequently, a further improvement in productivity has been difficult.

On the other hand, photosensitive compositions containing a modifiedpoly(vinyl alcohol) resin having radical-polymerizable pendant groupsgrafted to the polymer backbone are described in Japanese PatentLaid-Open No. 2000-181062 and International Patent Publication No.2000-506282. However, these compositions are not intended to be used forproducing lithographic printing plates. Furthermore, since thesephotosensitive compositions take advantage of the water solubilityinherent in poly(vinyl alcohol) so as to be developed with water, theyhave had the following problem when used as a binder for lithographicprinting plates. As the content of the radical-polymerizable groupsincorporated, which are effective in improving press life, is increased,the content of hydroxyl groups, which impart developability, becomes lowin proportion thereto, resulting in impaired developability. Namely, ithas been difficult to attain both high press life and developability.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to eliminate theabove-described drawbacks of the conventional art and to provide anegative photosensitive lithographic printing plate, especially onesuitable for drawing with a laser beam, from which a lithographicprinting plate having sufficient press life can be obtained with highproductivity without impairing developability even under such exposureconditions that the irradiation energy per unit area is low.

The present inventors made intensive investigations in order toaccomplish the object. As a result, it has been found that when amodified poly(vinyl alcohol) resin having a radical-polymerizable groupand an acid group is used as a polymeric binder serving as a componentof a photosensitive layer, then the object is accomplished.

(1) A negative photosensitive lithographic printing plate comprising:

a support; and

a photosensitive layer containing:

a modified poly(vinyl alcohol) resin binder having aradical-polymerizable group and an acid group; and

at least one of a photo-polymerization initiator and aheat-polymerization initiator.

(2) The negative photosensitive lithographic printing plate as describedin item (1), wherein the modified poly(vinyl alcohol) resin bindercontains: at least one of repeating units represented by formulae (I)and (II); and at least one of repeating units represented by formula(III):

wherein A and B each independently represents a radical-polymerizablegroup; X represents an acid group; R¹, R² and R³ each independentlyrepresents a substituted or unsubstituted hydrocarbon group having 1 to30 carbon atoms, and R¹, R²and R³ each has a valent of (m+1), (n+1) and(p+1) respectively; and m, n, and p each independently represents aninteger of 1 to 5.

(3) The negative photosensitive lithographic printing plate as describedin item (1), wherein the radical-polymerizable group has anaddition-polymerizable unsaturated bond.

(4) The negative photosensitive lithographic printing plate as describedin item (1), wherein the radical-polymerizable group has at least oneselected from the group consisting of a (meth)acryloyl group,(meth)acrylamide group, allyl group and styrene structure.

(5) The negative photosensitive lithographic printing plate as describedin item (1), wherein the acid group has an acid dissociation constant:pK_(a) of 7 or lower.

(6) The negative photosensitive lithographic printing plate as describedin item (1), wherein the acid group is selected from the groupconsisting of —COOH, —SO₃H, —OSO₃H, —PO₃H₂, —OPO₃H₂, —CONHSO₂— and—SO₂NHSO₂—.

(7) The negative photosensitive lithographic printing plate as describedin item (1), wherein the acid group is —COOH.

(8) The negative photosensitive lithographic printing plate as describedin item (2), wherein the repeating unit represented by formula (III) isrepresented by formula (IV):

wherein R³ represents a substituted or unsubstituted hydrocarbon grouphaving 1 to 30 carbon atoms, and R³ has a valent of (p+1); and prepresents an integer of 1 to 5.

(9) The negative photosensitive lithographic printing plate as describedin item (8), wherein R³ in the formula (IV) contains at least one of analiphatic ring structure and an aromatic ring structure.

(10) The negative photosensitive lithographic printing plate asdescribed in item (8), wherein R³ in the formula (IV) contains analiphatic ring structure.

(11) The negative photosensitive lithographic printing plate asdescribed in item (2), wherein the modified poly(vinyl alcohol) resinbinder contains:

i) at least one of the repeating units represented by formulae (I) and(II) in an amount of from 1 to 99% by mole; and

ii) at least one of repeating units represented by formula (III) in anamount of from 1 to 70% by mole,

in which the sum of the repeating unit i) and the repeating unit ii) is2 to 100% by mole.

(12) The negative photosensitive lithographic printing plate asdescribed in item (1), wherein the photosensitive layer further containsa compound having at least one ethylenically unsaturated bond capable ofundergoing an addition polymerization.

One of the features of the negative (negative working) photosensitivelithographic printing plate of the invention resides in that a modifiedpoly(vinyl alcohol) resin having a radical-polymerizable group and anacid group is used as a polymeric binder. Due to the use of this resin,the negative photosensitive lithographic printing plate of the inventioncan give a printing plate having sufficient press life with highproductivity without impairing developability even under such exposureconditions that the irradiation energy per unit area is low.

Although the reasons for this effect of the invention have not beenelucidated, the following may be thought. Besides having high mechanicalstrength, the modified poly(vinyl alcohol) resin is more apt to becrosslinked to cure in exposed areas due to the incorporation ofradical-polymerizable groups. As a result, sufficient press life can beobtained even in regions exposed at a low energy. Furthermore, due tothe acid groups incorporated simultaneously, the unexposed areas haveexcellent removability by alkali development. Thus, an excellentprinting plate which combines excellent productivity and press life canbe obtained without impairing developability.

DETAILED DESCRIPTION OF THE INVENTION

The photosensitive layer in the negative photosensitive lithographicprinting plate of the invention will be explained below in detail.

[Polymeric Binder]

The polymeric binder, which is characteristic of the invention, isexplained first.

The polymeric binder used in the photosensitive layer in the negativephotosensitive lithographic printing plate of the invention comprises amodified poly(vinyl alcohol) resin having a radical-polymerizable groupand an acid group. The modified poly(vinyl alcohol) resin having aradical-polymerizable group and an acid group is preferably a modifiedpoly(vinyl alcohol) resin having: a repeating unit containing at leastone of radical-polymerizable groups represented by formula (I) and (II);and a repeating unit containing at least one of acid groups representedby formula (III):

(wherein A and B each independently represent a radical-polymerizablegroup; X represents an acid group; R¹, R², and R³ independentlyrepresent optionally substituted hydrocarbon groups each having 1 to 30carbon atoms and respectively having valences of (m+1), (n+1), and(p+1); and m, n, and p each independently represent an integer of 1 to5).

Examples of the radical-polymerizable groups represented by A and Binclude addition-polymerizable unsaturated bonds (e.g., (meth)acryloylgroup, (meth)acrylamide group, (meth)acrylonitrile group, allyl group,styrene structure, vinyl ether structure, and acetylene structure), —SH,—PH, —SiH, —GeH, and a disulfide structure. Preferred from thestandpoint of press life are addition-polymerizable unsaturated bonds.More preferred of these are a (meth)acryloyl group, (meth)acrylamidegroup, allyl group, and styrene structure. The term: “(meth)acryloylgroup” herein means an acryloyl group or a methacryloyl group.

The acid group represented by X is not particularly limited. However, itis preferably an acid group having an acid dissociation constant(pK_(a)) of 7 or lower. The acid group is more preferably —COOH, —SO₃H,—OSO₃H, —PO₃H₂, —OPO₃H₂, —CONHSO₂—, or —SO₂NHSO₂—, and is mostpreferably —COOH.

Examples of the optionally substituted hydrocarbon groups represented byR¹, R², and R³, which each have 1 to 30 carbon atoms and respectivelyhave valences of (m+1), (n+1), and (p+1), include hydrocarbon groupsrespectively having valences of (m+1), (n+1), and (p+1), formed from thefollowing hydrocarbons, which may have one or more substituents, byremoving (m+1), (n+1), and (p+1) of the hydrogen atoms (including thehydrogen atoms on the substituents) from the following hydrocarbons.

Examples of the hydrocarbons include aliphatic hydrocarbons having 1 to30 carbon atoms, such as methane, ethane, propane, butane, hexane,nonane, decane, octadecane, cyclopentane, cyclohexane, adamantane,norbornane, decahydronaphthalene, tricyclo[5.2.1.0^(2,6)]decane,ethylene, propylene, 1-butene, 1-hexene, 1-heptadecene, 2-butene,2-hexene, 4-nonene, 7-tetradecene, butadiene, piperylene, 1,9-decadiene,cyclopentene, cyclohexene, cyclooctene, 1,4-cyclohexadiene,1,5-cyclooctadiene, 1,5,9-cyclododecatriene, norbornylene,octahydronaphthalene, bicyclo[2.2.]hepta-2,5-diene, acetylene,1-propyne, and 2-hexyne, and aromatichydrocarbons such as benzene,naphthalene, anthracene, indene, and fluorene.

In each of such hydrocarbon groups, one or more of the carbon atomsconstituting the group may have been replaced with heteroatoms selectedfrom oxygen, nitrogen, and sulfur atoms.

Examples of the substituents include monovalent atoms of nonmetallicelements excluding hydrogen and monovalent groups of atoms ofnonmetallic elements. Specific examples thereof include halogen atoms(—F, —Br, —Cl, and —I), hydroxyl, alkoxy groups, aryloxy groups,mercapto, alkylthio groups, arylthio groups, alkyldithio groups,aryldithio groups, amino, N-alkylamino groups, N,N-dialkylamino groups,N-arylamino groups, N,N-diarylamino groups, N-alkyl-N-arylamino groups,acyloxy groups, carbamoyloxy, N-alkylcarbamoyloxy groups,N-arylcarbamoyloxy groups, N,N-dialkylcarbamoyloxy groups,N,N-diarylcarbamoyloxy groups, N-alkyl-N-arylcarbamoyloxy groups,alkylsulfoxy groups, arylsulfoxy groups, acylthio groups, acylaminogroups, N-alkylacylamino groups, N-arylacylamino groups, ureido,N′-alkylureido groups, N′,N′-dialkylureido groups, N′-arylureido groups,N′,N′-diarylureido groups, N′-alkyl-N′-arylureido groups, N-alkylureidogroups, N-arylureido groups, N′-alkyl-N-alkylureido groups,N′-alkyl-N-arylureido groups, N′,N′-dialkyl-N-alkylureido groups,N′,N′-dialkyl-N-arylureido groups, N′-aryl-N-alkylureido groups,N′-aryl-N-arylureido groups, N′,N′-diaryl-N-alkylureido groups,N′,N′-diaryl-N-arylureido groups, N′-alkyl-N′-aryl-N-alkylureido groups,N′-alkyl-N′-aryl-N-arylureido groups, alkoxycarbonylamino groups,aryloxycarbonylamino groups, N-alkyl-N-alkoxycarbonylamino groups,N-alkyl-N-aryloxycarbonylamino groups, N-aryl-N-alkoxycarbonylaminogroups, N-aryl-N-aryloxycarbonylamino groups, formyl, acyl groups,carboxyl and its conjugate base group, alkoxycarbonyl groups,aryloxycarbonyl groups, carbamoyl, N-alkylcarbamoyl groups,N,N-dialkylcarbamoyl groups, N-arylcarbamoyl groups, N,N-diarylcarbamoylgroups, N-alkyl-N-arylcarbamoyl groups, alkylsulfinyl groups,arylsulfinyl groups, alkylsulfonyl groups, arylsulfonyl groups, sulfo(—SO₃H) and its conjugate base group, alkoxysulfonyl groups,aryloxysulfonyl groups, sulfinamoyl, N-alkylsulfinamoyl groups,N,N-dialkylsulfinamoyl groups, N-arylsulfinamoyl groups,N,N-diarylsulfinamoyl groups, N-alkyl-N-arylsulfinamoyl groups,sulfamoyl, N-alkylsulfamoyl groups, N,N-dialkylsulfamoyl groups,N-arylsulfamoyl groups, N,N-diarylsulfamoyl groups,N-alkyl-N-arylsulfamoyl groups, N-acylsulfamoyl groups and theirconjugate base groups, N-alkylsulfonylsulfamoyl groups (—SO₂NHSO₂(alkyl)) and their conjugate base groups, N-arylsulfonylsulfamoyl groups(—SO₂NHSO₂(aryl)) and their conjugate base groups,N-alkylsulfonylcarbamoyl groups (—CONHSO₂ (alkyl)) and their conjugatebase groups, N-arylsulfonylcarbamoyl groups (—CONHSO₂ (aryl)) and theirconjugate base groups, alkoxysilyl groups (—Si(O-alkyl)₃), aryloxysilylgroups (—Si(O-aryl)₃), hydroxysilyl (—Si(OH)₃) and its conjugate basegroup, phosphono (—PO₃H₂) and its conjugate base group, dialkylphosphonogroups (—PO₃(alkyl)₂), diarylphosphono groups (—PO₃(aryl)₂),alkylarylphosphono groups (—PO₃(alkyl)(aryl)), monoalkylphosphono groups(—PO₃H(alkyl)) and their conjugate base groups, monoarylphosphono groups(—PO₃H(aryl)) and their conjugate base groups, phosphonooxy (—OPO₃H₂)and its conjugate base group, dialkylphosphonooxy groups(—OPO₃(alkyl)₂), diarylphosphonooxy groups (—OPO₃(aryl)₂),alkylarylphosphonooxy groups (—OPO₃(alkyl) (aryl)),monoalkylphosphonooxy groups (—OPO₃H(alkyl)) and their conjugate basegroups, monoarylphosphonooxy groups (—OPO₃H(aryl)) and their conjugatebase groups, cyano, nitro, dialkylboryl groups (—B(alkyl)₂), diarylborylgroups (—B(aryl)₂), alkylarylboryl groups (—B(alkyl)(aryl)),dihydroxyboryl (—B(OH)₂) and its conjugate base group, alkylhydroxyborylgroups (—B(alkyl)(OH)) and their conjugate base groups, arylhydroxyborylgroups (—B(aryl)(OH)) and their conjugate base groups, aryl groups,alkyl groups, alkenyl groups, and alkynyl groups.

These substituents may be bonded to each other or to the substitutedhydrocarbon group to form a ring. The substituents may be furthersubstituted.

Preferred examples of the substituents include halogen atoms, alkoxygroups, aryloxy groups, alkyl groups, alkenyl groups, alkynyl groups,and aryl groups.

The repeating units represented by formulae (I) and (II), which containone or more radical-polymerizable groups, can be incorporated bysubjecting a compound having both a hydroxyl-reactive functional groupand a group capable of undergoing a radical reaction and a poly(vinylalcohol) resin to a polymer reaction. Examples of the hydroxyl-reactivegroup include an aldehyde group, which undergoes an acetalizationreaction, an epoxy group, which undergoes a ring-opening reaction, anisocyanate group, which undergoes a urethane-forming reaction, and acarboxylic acid, acid halide, or acid anhydride, which undergoes anesterification reaction.

Examples of such a compound having both a hydroxyl-reactive functionalgroup and a group capable of undergoing a radical reaction include thealdehydes shown in Japanese Patent Laid-Open No. 2000-181062 andInternational Patent Publication No. 2000-506282, glycidyl(meth)acrylate, (meth)acryloylisocyanates, (meth)acryloyloxyethylisocyanate, (meth)acrylic acid, (meth)acrylic anhydride, (meth)acryloylchloride, and the following compounds.

Preferred of the repeating units represented by formulae (I) and (II),which contain one or more radical-polymerizable groups, are repeatingunit represented by formula (I) which have a structure formed from analdehyde through acetalization, because these repeating units bringabout high press life.

The binder polymer may contain one kind or two or more kinds ofrepeating units represented by formula (I) and/or (II), which containone or more radical-polymerizable groups.

The total content of the repeating units represented by formula (I)and/or (II), which contain one or more radical-polymerizable groups, inthe modified poly(vinyl alcohol) resin is suitably determined accordingto the structure of the resin, design of the photosensitive layer,properties of the developing solution to be used, etc. However, from thestandpoint of press life, the total content thereof is preferably from 1to 99% by mole, more preferably from 5 to 90% by mole, even morepreferably from 10 to 80% by mole, most preferably from 20 to 70% bymole.

Especially preferred of the repeating units represented by formula(III), which contain one or more acid groups, are repeating unitsrepresented by formula (IV), because the modified poly(vinyl alcohol)resin having these repeating units is easy to synthesis. The repeatingunits represented by formula (IV) can be incorporated by subjecting ananhydride represented by the following formula (V) and a poly(vinylalcohol) resin to a polymer reaction.

(In formulae (IV) and (V), R³ is the same as in formula (III).)

Examples of the acid anhydride include succinic anhydride,methylsuccinic anhydride, isobutynylsuccinic anhydride,2-octen-1-ylsuccinic anhydride, S-acetylmercaptosuccinic anhydride,phenylsuccinic anhydride, itaconic anhydride, diacetyltartaricanhydride, maleic anhydride, citraconic anhydride, bromomaleicanhydride, dichloromaleic anhydride, phenylmaleic anhydride, aconiticanhydride, glutaric anhydride, 3-ethyl-3-methylglutaric anhydride,3,3-tetramethyleneglutaric anhydride, hexafluoroglutaric anhydride,2-phenylglutaric anhydride, 3,5-diacetyltetrahydropyran-2,4,6-trione,diglycolic anhydride, 3-oxabicyclo[3.1.0]hexane-2,4-dione,cyclohexanedicarboxylic anhydride, hexahydro-4-methylphthalic anhydride,1,2,3,6-tetrahydrophthalic anhydride, 3,4,6-tetrahydrophthalicanhydride, 5-norbornene-2,3-dicarboxylic anhydride,bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride, cantharidin,3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride,1-cyclopentene-1,2-dicarboxylic anhydride,1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic anhydride, phthalicanhydride, isatic anhydride, homophthalic anhydride, 4-methylphthalicanhydride, 3,6-difluorophthalicanhydride, 3-hydroxyphthalicanhydride,1,2,4-benzenetricarboxylic anhydride, 3-nitrophthalic anhydride,diphenic anhydride, 1,8-naphthalic anhydride, 4-aminonaphthalicanhydride, and 4-amino-3,6-disulfo-1,8-naphthalic anhydride dipotassiumsalt.

From the standpoint of press life, R³ is preferably a group having analiphatic or aromatic ring structure, especially a group having analiphatic ring structure.

The binder polymer may contain one kind or two or more kinds ofrepeating units represented by formula (IV), which have one or morecarboxyl groups.

The total content of the repeating units represented by formula (IV),which contain one or more carboxyl groups, in the modified poly(vinylalcohol) resin is suitably determined according to the structure of theresin, design of the photosensitive layer, properties of the developingsolution to be used, etc. However, from the standpoint of press life,the total content thereof is preferably from 1 to 70% by mole, morepreferably from 5 to 60% by mole, most preferably from 10 to 50% bymole.

Preferred examples of the units represented by formulae (I), (II), and(IV) are shown below, but they should not be construed as limiting thescope of the invention.

EXAMPLES OF FORMULA (I)

EXAMPLES OF FORMULA (II)

R⁵: H or Me

R⁶: H or R⁴

EXAMPLES OF FORMULA (IV)

Although the modified poly(vinyl alcohol) resin to be used in theinvention may be one in which all the hydroxyl groups have beenmodified, it usually contains vinyl alcohol repeating units remainingunreacted. From the standpoint of press life, the content of vinylalcohol repeating units is generally from 0 to 90% by mole, preferablyfrom 0 to 60% by mole, more preferably from 0 to 40% by mole.

The modified poly(vinyl alcohol) resin can contain vinyl acetaterepeating units depending on the degree of saponification of thepoly(vinyl alcohol) used as a starting material. The content of vinylacetate repeating units is preferably from 0 to 50% by mole, morepreferably from 0 to 40% by mole, most preferably from 0 to 30% by mole,from the standpoint of ease of incorporation of units represented byformulae (I), (II), and (III). The modified poly(vinyl alcohol) resinmay be a copolymer with vinylpyrrolidone or the like.

The modified poly(vinyl alcohol) resin binder in the invention is mostpreferably one which contains at least one of repeating unitsrepresented by formula (I) and at least one of repeating unitsrepresented by formula (IV).

The molecular weight of the modified poly(vinyl alcohol) resin binder inthe invention is suitably determined from the standpoints ofimage-forming properties and press life. In general, higher molecularweights bring about better press life but tend to result in impairedimage-forming properties. Conversely, lower molecular weights bringabout improved image-forming properties but reduce press life. Themolecular weight thereof is preferably from 2,000 to 1,000,000, morepreferably from 5,000 to 500,000, most preferably from 10,000 to200,000.

The negative photosensitive lithographic printing plate in the inventionmay use one kind of the modified poly(vinyl alcohol) resin binder, ormay use in combination of two or more kinds thereof. Furthermore, amixture of this binder and one or more known polymeric binders may beused. In the case of using such a mixture, known polymeric binders maybe added in an amount generally from 1 to 60% by weight, preferably from1 to 40% by weight, more preferably from 1 to 20% by weight, based onthe total amount of all polymeric binders used. Known polymeric binderscan be used as such optional polymeric binders without particularlimitations. Preferred examples thereof include binders frequently usedin the art, such as binders having an acrylic main chain, urethanebinders, and acetal-modified poly(vinyl alcohol) resins (e.g., butyralresins).

Although the total amount of the modified poly(vinyl alcohol) resinbinder and one or more optional polymeric binders in the photosensitivelayer can be suitably determined, it is generally from 10 to 90% byweight, preferably from 20 to 80% by weight, more preferably from 30 to70% by weight, based on the total amount of all nonvolatile ingredientsin the photosensitive layer.

[Photo- or Heat-Polymerization Initiator]

As the photopolymerization initiator, various known photopolymerizationinitiators shown in patent and other documents, or a combination of twoor more of these (photopolymerization initiator system) can be suitablyselected according to the wavelength for the light source to be used.

Various photopolymerization initiators (initiator systems) have beenproposed for use in the case of using a blue semiconductor laser, an Arlaser, the second higher harmonic of an infrared semiconductor laser, oran SHG-YAG laser as a light source. Examples thereof include the photoreducible dyes of some kind shown in, e.g., U.S. Pat. No. 2,850,445,such as Rose Bengal, Eosin, and erythrocine; a system comprising acombination of a dye and an initiator, e.g., a combination of a dye andan amine (see Japanese Patent Publication No. 20189/1969); a systemcomprising a combination of a hexaarylbiimidazole, a radical generator,and a dye (see Japanese Patent Publication No. 37377/1970); a systemcomprising a hexaarylbiimidazole and a p-dialkylaminobenzylidene ketone(see Japanese Patent Publication No. 2528/1972 and Japanese PatentLaid-Open No. 155292/1979); a system comprising a cycliccis-α-dicarbonyl compound and a dye (see Japanese Patent Laid-Open No.84183/1973); a system comprising a cyclic triazine and a merocyanine dye(see Japanese Patent Laid-Open No. 151024/1979); a system comprising3-ketocoumarin and an activator (see Japanese Patent Laid-Open Nos.112681/1977 and 15503/1983); a system comprising biimidazole, a styrenederivative, and a thiol (see Japanese Patent Laid-Open No. 140203/1984);a system comprising an organic peroxide and a dye (see Japanese PatentLaid-Open Nos. 1504/1984, 140203/1984, 189340/1984, and 174203/1987,Japanese Patent Publication No. 1641/1987, and U.S. Pat. No. 4,766,055);a system comprising a dye and an active halogen compound (see JapanesePatent Laid-Open Nos. 1718105/1988, 258903/1988, and 264771/1991); asystem comprising a dye and a borate compound (see Japanese PatentLaid-Open Nos. 143044/1987, 150242/1987, 13140/1989, 13141/1989,13142/1989, 13143/1989, 13144/1989, 17048/1989, 229003/1989,298348/1989, and 138204/1989); a system comprising a dye having arhodanine ring and a radical generator (see Japanese Patent Laid-OpenNos. 179643/1990 and 244050/1990); a system comprising a titanocene anda 3-ketocoumarin dye (see Japanese Patent Laid-Open No. 221110/1988); asystem comprising a combination of a titanocene, a xanthene dye, and anaddition-polymerizable ethylenically unsaturated compound containing anamino or urethane group (see Japanese Patent Laid-Open Nos. 221958/1992and 219756/1992); a system comprising a titanocene and a specificmerocyanine dye (see Japanese Patent Laid-Open No. 295061/1994); and asystem comprising a titanocene and a dye having a benzopyran ring (seeJapanese Patent Laid-Open No. 334897/1996).

Especially preferred photopolymerization initiators (initiator systems)in the photosensitive layer in the negative photosensitive lithographicprinting plate of the invention contain at least one titanocene.

Any titanocene compound may be used in the photopolymerization initiator(initiator system) in the invention as long as the titanocene compoundis capable of generating an active radical upon irradiation with a lightin the presence of a sensitizing dye. One or more titanocene compoundsto be used in the invention may be suitably selected from the knowntitanocene compounds described in, e.g., Japanese Patent Laid-Open Nos.152396/1984, 151197/1986, 41483/1988, 41484/1988, 249/1990, 291/1990,27393/1991, 12403/1991, and 41170/1994.

Specific examples of the titanocene compounds includedicyclopentadienyltitanium dichloride,dicyclopentadienyltitanium-bisphenyl,dicyclopentadienyltitanium-bis-2,3,4,5,6-pentafluorophen-1-yl(hereinafter referred to also as “T-1”),dicyclopentadienyltitanium-bis-2,3,5,6-tetrafluorophen-1-yl,dicyclopentadienyltitanium-bis-2,4,6-trifluorophen-1-yl,dicyclopentadienyltitanium-bis-2,6-difluorophen-1-yl,dicyclopentadienyltitanium-bis-2,4-difluorophen-1-yl,dimethylcyclopentadienyltitanium-bis-2,3,4,5,6-pentafluorophen-1-yl,dimethylcyclopentadienyltitanium-bis-2,3,5,6-tetrafluorophen-1-yl,dimethylcyclopentadienyltitanium-bis-2,4-difluorophen-1-yl, andbis(cyclopentadienyl)bis(2,6-difluoro-3-(pyr-1-yl)phenyl)titanium(hereinafter referred to also as “T-2”).

Those titanocene compounds can be chemically modified in various ways inorder to improve the properties of the photosensitive layer. Examples ofusable modification techniques include bonding to a radical-generatingpart of, e.g., a sensitizing dye or addition-polymerizable unsaturatedcompound, incorporation of a hydrophilic group, improvement ofcompatibility, incorporation of a substituent for inhibiting crystalprecipitation, incorporation of a substituent for improving adhesion,and conversion into a polymer.

Methods for using those titanocene compounds also can be suitablydetermined without particular limitations according to the performancedesign of the negative photosensitive lithographic printing plate, as inthe case of the addition-polymerizable compounds described above. Forexample, a titanocene compound can have enhanced compatibility in thephotosensitive layer when used in combination with one or more othertitanocene compounds. Larger amounts of the photopolymerizationinitiators to be used, including the titanocene compounds, are usuallyadvantageous from the standpoint of photosensitivity. Sufficientphotosensitivity is obtained when a photopolymerization initiator isused in an amount of generally from 0.5 to 80 parts by weight,preferably from 1 to 50 parts by weight, per 100 parts by weight of thenonvolatile ingredients in the photosensitive layer. On the other hand,smaller titanocene amounts are preferred from the standpoint ofdiminishing the blurring caused by a light of around 500 nm as a resultof the use of yellow or white light or the like; these light are for amajor purpose of the invention. Even when the amount of one or moretitanocene compounds is reduced to 6 parts by weight or smaller,especially to 1.9 parts by weight or smaller, and further to 1.4 partsby weight or smaller, sufficient photosensitivity can be obtained byusing the titanocene compounds in combination with the other sensitizingdye.

In the case where a laser which emits infrared rays having a wavelengthof from 760 to 1,200 nm is to be used as a light source, it is generallyindispensable to use an infrared absorber. Infrared absorbers functionto absorb infrared rays and convert them into heat. A radical generatoris pyrolyzed by the resultant heat to generate a radical. The infraredabsorber to be used in the invention is a dye or pigment having anabsorption maximum in the wavelength range of from 760 to 1,200 nm.

As the dye can be used commercial dyes and other known dyes shown in theliterature, e.g., Senryô Binran (edited by Japan Society of OrganicSynthesis Chemistry, published in 1970). Examples of the dyes includeazo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinonedyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes,qunoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyryliumsalts, and metal thiolate complexes.

Preferred examples of the dyes include the cyanine dyes described in,e.g., Japanese Patent Laid-Open Nos. 125246/1983, 84356/1984,202829/1984, and 78787/1985; the methine dyes described in, e.g.,Japanese Patent Laid-Open Nos. 173696/1983, 181690/1983, and194595/1983; the naphthoquinone dyes described in, e.g., Japanese PatentLaid-Open Nos. 112793/1983, 224793/1983, 48187/1984, 73996/1984,52940/1985, and 63744/1985; the squarylium dyes described in, e.g.,Japanese Patent Laid-Open No. 112792/1983; and the cyanine dyesdescribed in British Patent 434,875.

Other preferred examples thereof include the near-infrared-absorbingsensitizer described in U.S. Pat. No. 5,156,938; the substitutedarylbenzo(thio)pyrylium salts described in U.S. Pat. No. 3,881,924; thetrimethine thiapyrylium salts described in Japanese Patent Laid-Open No.142645/1982 (U.S. Pat. No. 4,327,169); the pyrylium compounds describedin Japanese Patent Laid-Open Nos. 181051/1983, 220143/1983, 41363/1984,84248/1984, 84249/1984, 146063/1984, and 146061/1984; the cyanine dyesdescribed in Japanese Patent Laid-Open No. 216146/1984; the pentamethinethiopyrylium salts described in U.S. Pat. No. 4,283,475; and thepyrylium compounds disclosed in Japanese Patent Publication Nos.13514/1993 and 19702/1993.

Further preferred examples of the dyes include thenear-infrared-absorbing dyes shown by formulae (I) and (II) in thespecification of U.S. Pat. No. 4,756,993.

Especially preferred of those dyes are cyanine dyes, squarylium dyes,pyrylium salts, and nickel thiolate complexes. More preferred arecyanine dyes. In particular, the cyanine dyes represented by thefollowing formula (VI) are most preferred.

In formula (VI), X¹ represents a halogen atom or X²—L¹, wherein X²represents an oxygen atom or sulfur atom and L¹ represents a hydrocarbongroup having 1 to 12 carbon atoms. R⁷ and R⁸ each independentlyrepresent a hydrocarbon group having 1 to 12 carbon atoms. From thestandpoint of the storage stability of a coating fluid forphotosensitive-layer formation, R⁷ and R⁸ preferably are hydrocarbongroups having 2 or more carbon atoms, and more preferably are bonded toeach other to form a five- or six-membered ring.

Ar¹ and Ar² may be the same or different and each represent an aromatichydrocarbon group which may have one or more substituents. Preferredexamples of the aromatic hydrocarbon group include a benzene ring and anaphthalene ring. Preferred examples of the substituents includehydrocarbon groups having up to 12 carbon atoms, halogen atoms, andalkoxy groups having up to 12 carbon atoms. Y¹ and Y² may be the same ordifferent and each represent a sulfur atom or dialkylmethylene grouphaving up to 12 carbon atoms. R⁹ and R¹⁰ maybe the same or different andeach represent a hydrocarbon group which has up to 20 carbon atoms andmay have one or more substituents. Preferred examples of thesubstituents include alkoxy groups having up to 12 carbon atoms,carboxyl, and sulfo. R¹¹, R¹², R¹³, and R¹⁴ may be the same or differentand each represent a hydrogen atom or a hydrocarbon group having up to12 carbon atoms. From the standpoint of availability of startingmaterials, R¹¹ to R¹⁴ are preferably hydrogen atoms. Z¹⁻ represents acounter anion, provided that Z¹⁻ need not be present when any of R⁷ toR¹⁴ has been substituted with a sulfo group. From the standpoint of thestorage stability of a coating fluid for photosensitive-layer formation,Z¹⁻ is preferably a halogen ion, perchlorate ion, tetrafluoroborate ion,hexafluorophosphate ion, or sulfonate ion, and is more preferably aperchlorate ion, hexafluorophosphate ion, or arylsulfonate ion.

Specific examples of the cyanine dyes represented by formula (VI), whichcan be advantageously used in the invention, include those shown below.These dyes are given in the specification of Japanese Patent ApplicationNo. 310623/1999.

As the pigment in the invention can be used commercial pigments andpigments described in a Color Index (C.I.) handbook, Saishin GanryôBinran (edited by Japan Society of Pigment Technology, published in1977), Saishin Ganryô Ôyô Gijutsu (CMC Shuppan, published in 1986), andInsatsu Inki Gijutsu (CMC Shuppan, published in 1984).

Examples of the kinds of such pigments include black pigments, yellowpigments, orange pigments, brown pigments, red pigments, purplepigments, blue pigments, green pigments, fluorescent pigments, metalpowder pigments, and polymer-bonded pigments. Specific examples ofusable pigments include insoluble azo pigments, azo lake pigments,condensation azo pigments, chelate azo pigments, phthalocyaninepigments, anthraquinone pigments, perylene pigments, perinone pigments,thioindigo pigments, quinacridone pigments, dioxazine pigments,isoindolinone pigments, quinophthalone pigments, dyeing lake pigments,azine pigments, nitroso pigments, nitro pigments, natural pigments,fluorescent pigments, inorganic pigments, and carbon black. Preferred ofthese pigments is carbon black.

Those pigments maybe used without undergoing a surface treatment, or maybe used after having undergone a surface treatment. Possible methods forsurface treatment include a technique in which the surface of a pigmentis coated with a resin or wax, a technique in which a surfactant isadhered to the surface of a pigment, and a technique in which a reactivesubstance (e.g., a silane coupling agent, epoxy compound, orpolyisocyanate) is bonded to the surface of a pigment. These methods forsurface treatment are described in Kinzoku Sekken No Seishitsu To Ôyô(Saiwai Shobo), Insatsu Inki Gijutsu (CMC Shuppan, published in 1984),and Saishin Ganryô Ôyô Gijutsu (CMC Shuppan, published in 1986).

The particle diameter of the pigment is preferably from 0.01 to 10 μm,more preferably from 0.05 to 1 μm, most preferably from 0.1 to 1 μm. Useof a pigment having a particle diameter smaller than 0.01 μm isundesirable in that the pigment dispersion shows poor stability in acoating fluid for forming an image-forming photosensitive layer. On theother hand, use of a pigment having a particle diameter exceeding 10 μmis undesirable from the standpoint of the evenness of the image-formingphotosensitive layer to be formed.

For dispersing the pigment, known dispersion techniques for theproduction of inks, toners, or the like can be used. Examples of usabledispersing machines include an ultrasonic disperser, sand mill,attritor, pearl mill, supermill, ball mill, impeller, disperser, KDmill, colloid mill, dynatron, three-roll mill, and pressure kneader.Details thereof are given in Saishin Ganryô Ôyô Gijutsu (CMC Shuppan,published in 1986).

Such infrared absorbers may be incorporated into either thephotosensitive layer or another layer, e.g., an overcoat layer orundercoat layer. It is, however, preferred that in the negativephotosensitive lithographic printing plate finally produced, thephotosensitive layer should have an optical density of from 0.1 to 3.0as measured at the wavelength corresponding to the absorption maximumthereof in the wavelength range of from 760 to 1,200 nm. Opticaldensities thereof outside the range tend to result in reducedsensitivity. Since the optical density of the photosensitive layer isdetermined by the amount of the infrared absorber added thereto and thethickness of the layer, a desired value of optical density can beobtained by regulating the two factors. The optical density of aphotosensitive layer can be measured by an ordinary method. Examples ofthe method for measurement include: a method in which a photosensitivelayer is formed by coating on a transparent or white support in such anamount as to result in a suitably predetermined dry thickness within therange required for lithographic printing plates and is then examinedwith a transmission type optical densitometer; and a method in which aphotosensitive layer is formed on a reflective support such as analuminum support and examined for reflection density.

As a heat-polymerization initiator, a heat-decomposable radicalgenerator is used in combination with the infrared absorber. Thisradical generator means a compound which generates a radical uponirradiation with infrared laser beam. Examples of the radical generatorinclude onium salts, triazine compounds having a trihalomethyl group,peroxides, azo polymerization initiators, azide compounds, andquinonediazide. Of these, onium salts are preferred because of theirhigh sensitivity.

Preferred onium salts which can be advantageously used as a radicalpolymerization initiator in the invention are explained below. Examplesof the preferred onium salts include iodonium salts, diazonium salts,and sulfonium salts. In the invention, these onium salts do not functionas an acid generator but as an initiator for radical polymerization. Theonium salts which can be advantageously used in the invention arerepresented by the following formulae (VII) to (IX).

Ar¹¹—I⁺—Ar¹² Z¹¹⁻  Formula (VII)

Ar²¹—N⁺≡N Z²¹⁻  Formula (VIII)

In formula (VII), Ar¹¹ and Ar¹² each independently represent anoptionally substituted aryl group having up to 20 carbon atoms(including the carbon atoms of any substituent). In the case where thisaryl group has one or more substituents, preferred examples of thesubstituents include halogen atoms, nitro, alkyl groups having up to 12carbon atoms, alkoxy groups having up to 12 carbon atoms, and aryloxygroups having up to 12 carbon atoms. Z¹¹⁻ represents a counter ionselected from the group consisting of a halogen ion, perchlorate ion,tetrafluoroborate ion, hexafluorophosphate ion, and sulfonate ion, andis preferably a perchlorate ion, hexafluorophosphate ion, orarylsulfonate ion.

In formula (VIII), Ar²¹ represents an optionally substituted aryl grouphaving up to 20 carbon atoms (including the carbon atoms of anysubstituent). Preferred examples of the substituents include halogenatoms, nitro, alkyl groups having up to 12 carbon atoms, alkoxy groupshaving up to 12 carbon atoms, aryloxy groups having up to 12 carbonatoms, alkylamino groups having up to 12 carbon atoms, dialkylaminogroups having up to 12 carbon atoms, arylamino groups having up to 12carbon atoms, and diarylamino groups having up to 12 carbon atoms. Z²¹⁻represents a counter ion, which has the same meaning as Z¹¹⁻.

In formula (IX), R³¹, R³², and R³³ may be the same or different and eachrepresent an optionally substituted hydrocarbon group having up to 20carbon atoms (including the carbon atoms of any substituent). Preferredexamples of the substituents include halogen atoms, nitro, alkyl groupshaving up to 12 carbon atoms, alkoxy groups having up to 12 carbonatoms, and aryloxy groups having up to 12 carbon atoms. Z³¹⁻ representsa counter ion, which has the same meaning as Z¹¹⁻.

Specific examples of the onium salts advantageously usable as a radicalgenerator in the invention include the following onium salts, which aregiven in the specification of Japanese Patent Application No.310623/1999.

The heat-decomposable radical generators for use in the invention have amaximum absorption wavelength of preferably 400 nm or shorter, morepreferably 360 nm or shorter. By using such a radical generator havingan absorption wavelength within the ultraviolet region, the negativephotosensitive lithographic printing plate can be handled in whitelight.

Those heat-decomposable radical generators can be added to a coatingfluid for photosensitive-layer formation in an amount of generally from0.1 to 50% by weight, preferably from 0.5 to 30% by weight, morepreferably from 1 to 20% by weight, based on all the nonvolatileingredients contained in the coating fluid for photosensitive-layerformation. Addition amounts thereof smaller than 0.1% by weight resultin poor sensitivity, while addition amounts thereof exceeding 50% byweight result in a printing plate in which the nonimage areas are soiledduring printing. Those radical generators may be used alone or incombination of two or more thereof. The heat-decomposable radicalgenerators may be added to the same layer as other ingredients or may beadded to a layer separately formed. However, it is preferred to add theradical generators to the same layer as other ingredients.

Ingredients which can be incorporated besides the polymeric binders andpolymerization initiators into the photosensitive layer will beexplained next.

The photosensitive layer in the negative photosensitive lithographicprinting plate of the invention contains a negative type photosensitivematerial for image formation. As this photosensitive material, a knownone can be used without particular limitations. Examples of the negativetype photosensitive material include the radical-polymerizable type, thecationically polymerizable type, and the hybrid type which undergoesboth radical polymerization and cationic polymerization. However,radical-polymerizable photosensitive materials are especially preferredbecause they have an excellent balance between sensitivity andstability.

The negative photosensitive lithographic printing plate of the inventionis especially suitable for plate making through direct drawing with alaser beam having a wavelength of from 300 to 1,200 nm. The printingplate thus produced there from has higher press life than conventionallithographic printing plates.

[Photo- or Heat-Polymerizable Negative Type Photosensitive Layer]

An especially preferred photosensitive layer in the negativephotosensitive lithographic printing plate of the invention is a photo-or heat-polymerizable negative type photosensitive layer comprising themodified poly(vinyl alcohol) resin binder, a photo- orheat-polymerization initiator, and a compound having at least oneethylenically unsaturated bond capable of undergoing additionpolymerization (hereinafter often referred to simply as“addition-polymerizable compound”). Besides these ingredients, variousadditives may be incorporated into this photosensitive layer, such as aco-sensitizer, colorant, plasticizer, and polymerization inhibitor.

[Addition-Polymerizable Compound]

The addition-polymerizable compound having at least one ethylenicallyunsaturated double bond to be used in the photo- or heat-polymerizablenegative type photosensitive layer is selected from compounds having atleast one, preferably two ethylenically unsaturated terminal bonds. Suchcompounds are widely known in this industrial field, and can be used inthe invention without particular limitations. Such compounds are in thechemical forms of, for example, monomer, prepolymers, i.e., dimer,trimer, and oligomer, and mixtures and copolymers thereof. Examples ofthe monomeric compounds and copolymers thereof include unsaturatedcarboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid,crotonic acid, isocrotonic acid, and maleic acid) and esters and amidesthereof. Preferred of these are esters of an unsaturated carboxylic acidwith an aliphatic polyhydric alcohol compound and amides of anunsaturated carboxylic acid with an aliphatic polyamine compound. Alsopreferred are: adducts of an unsaturated carboxylic acid ester or amidehaving a nucleophilic substituent, e.g., a hydroxyl, amino, or mercaptogroup, with a mono- or polyfunctional isocyanate or epoxy; and productsof the dehydrating condensation reaction of the ester or amide with amono- or polycarboxylic acid. Preferred examples of theaddition-polymerizable compound further include: adducts of anunsaturated carboxylic acid ester or amide having an electrophilicsubstituent, e.g., an isocyanate or epoxy group, with a mono- orpolyfunctional alcohol, amine, or thiol; and products of thesubstitution reaction of an unsaturated carboxylic acid ester or amidehaving an eliminable substituent, e.g., a halogen or a tosyloxy group,with a mono- or polyfunctional alcohol, amine, or thioether. Otherusable examples of the addition-polymerizable compound include compoundsformed by the reactions described above wherein an unsaturatedphosphonic acid, styrene, vinyl ether, or the like is used in place ofthe unsaturated carboxylic acid.

Specific examples of the monomeric esters of aliphatic polyhydricalcohol compounds with unsaturated carboxylic acids are as follows.Examples of the acrylic esters include ethylene glycol diacrylate,triethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethyleneglycol diacrylate, propylene glycol diacrylate, neopentyl glycoldiacrylate, trimethylolpropane triacrylate, trimethylolpropanetri(acryloyloxypropyl) ether, trimethylolethanetriacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri(acryloyloxyethyl) isocyanurate, and polyester acrylate oligomers.

Examples of the methacrylic esters include tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylme thane, andbis[p-(methacryloxyethoxy)phenyl]dimethylmethane.

Examples of the itaconic esters include ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate, and sorbitol tetraitaconate.

Examples of the crotonic esters include ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, andsorbitol tetradicrotonate.

Examples of the isocrotonic esters include ethylene glycoldiisocrotonate, pentaerythritol diisocrotonate, and sorbitoltetraisocrotonate.

Examples of the maleic esters include ethylene glycol dimaleate,triethylene glycol dimaleate, pentaerythritol dimaleate, and sorbitoltetramaleate.

Other preferred examples of the esters include the aliphatic alcoholesters shown in Japanese Patent Publication Nos. 27926/1971 and47334/1976 and Japanese Patent Laid-Open No. 196231/1982, the estershaving an aromatic framework shown in Japanese Patent Laid-Open Nos.5240/1984, 5241/1984, and 226149/1990, and the esters having an aminogroup shown in Japanese Patent Laid-Open No. 165613/1989.

The ester monomers shown above may be used as a mixture of two or morethereof.

Examples of the monomeric amides of an aliphatic polyamine compound withan unsaturated carboxylic acid include methylenebisacrylamide,methylenebismethacrylamide, 1,6-hexamethylenebisacrylamide,1,6-hexamethylenebismethacrylamide, diethylenetriaminetrisacrylamide,xylylenebisacrylamide, and xylylenebismethacrylamide.

Examples of other preferred amide monomers include those having acyclohexylene structure shown in Japanese Patent Publication No.21726/1979.

Also preferred are addition-polymerizable urethane compounds produced bythe addition reaction of an isocyanate with hydroxyl groups. Examplesthereof include the vinyl urethane compounds containing two or morepolymerizable vinyl groups per molecule described in, e.g., JapanesePatent Publication No. 41708/1973. The vinyl urethane compounds areproduced by causing a polyisocyanate compound having two or moreisocyanate groups per molecule to add a hydroxyl-containing vinylmonomer represented by the following formula (X):

CH₂═C(R⁴)COOCH₂CH(R⁵)OH  (X)

wherein R⁴ and R⁵ each represent H or CH₃.

Other preferred addition-polymerizable urethane compounds includeurethane acrylates such as those described in Japanese Patent Laid-OpenNo. 37193/1976 and Japanese Patent Publication Nos. 32293/1990 and16765/1990 and the urethane compounds having an ethylene oxide backbonedescribed in Japanese Patent Publication Nos. 49860/1983, 17654/1981,39417/1987, and 39418/1987.

Furthermore, use of the addition-polymerizable compounds having in themolecule an amino structure or sulfide structure described in JapanesePatent Laid-Open Nos. 277653/1988, 260909/1988, or 105238/1989 iseffective in obtaining a photopolymerizable composition having anexceedingly high photosensitization speed.

Other examples of the addition-polymerizable compound include polyesteracrylates such as those described in Japanese Patent Laid-Open No.64183/1973 and Japanese Patent Publication Nos. 43191/1974 and30490/1977 and polyfunctional acrylates or methacrylates such as epoxyacrylates obtained by reacting an epoxy resin with (meth)acrylic acid.The examples further include the specific unsaturated compoundsdescribed in Japanese Patent Publication Nos. 43946/1971, 40337/1989,and 40336/1989 and the vinylphosphonic acid compounds described inJapanese Patent Laid-Open No. 25493/1990. In some cases, the structurehaving a perfluoroalkyl group described in Japanese Patent Laid-Open No.22048/1986 is advantageously used. Also usable are the photocurablemonomers and oligomers shown in Nihon Setchaku Kyôkai-shi, Vol. 20, No.7, pp. 300-308 (1984).

Details of such addition-polymerizable compounds concerning thestructures thereof and the methods of use, e.g., as to whether theaddition-polymerizable compounds are used alone or in combination, theamount thereof to be added, etc., can be suitably determined withoutparticular limitations according to the performance design of thenegative photosensitive lithographic printing plate to be finallyobtained. For example, selections are made from the followingstandpoints. From the standpoint of photosensitization speed, structureshaving a high unsaturated-group content per molecule are preferred. Inmany cases, addition-polymerizable compounds having a functionality of 2or higher are preferred. From the standpoint of increasing the strengthof the image areas, i.e., the cured film, it is preferred to use anaddition-polymerizable compound having a functionality of 3 or higher. Atechnique effective in regulating both photosensitivity and strength isto use a combination of addition-polymerizable compounds differing infunctionality or polymerizable group (e.g., acrylic esters, methacrylicesters, styrene compounds, and vinyl ether compounds). Compounds havinga high molecular weight and compounds having high hydrophobicity bringabout a high photosensitization speed and excellent film strength but,in some cases, are undesirable from the standpoints of the rate ofdevelopment and precipitation from a developing solution. Furthermore,the selection of addition-polymerizable compounds and the method ofusing the same are important factors which influence the compatibilityand dispersibility thereof in other ingredients in the photosensitivelayer (e.g., the binder polymer, initiator, and colorant). For example,use of a low-purity compound or use of a combination of two or moreaddition-polymerizable compounds can improve compatibility.

There also are cases where an addition-polymerizable compound having aspecific structure is selected in order to improve adhesion to, e.g.,the support or the overcoat layer which will be described later. Withrespect to the proportion of the addition-polymerizable compounds in thephotosensitive layer, higher proportions are advantageous from thestandpoint of sensitivity. However, too high proportions thereof poseproblems such as the occurrence of undesirable phase separation,troubles in production steps due to tackiness of the photosensitivelayer (e.g., production failures attributable to the transfer oradhesion of photosensitive-layer components), and precipitation from adeveloping solution. From these standpoints, the addition-polymerizablecompounds are used in an amount of preferably from 5 to 80% by weight,more preferably from 25 to 75% by weight, based on the nonvolatileingredients in the photosensitive layer. The addition-polymerizablecompounds may be used alone or in combination of two or more thereof.Furthermore, addition-polymerizable compounds having an appropriatestructure may be selected and incorporated in an appropriate amountwithout particular limitations from the standpoints of the degree ofpolymerization inhibition by oxygen, resolution, blurring, change inrefractive index, surface tackiness, etc. In some cases, a coatingmethod for forming a layer constitution containing an undercoat layerand an overcoat layer may be employed.

[Co-Sensitizer]

The sensitivity of the photopolymerizable photosensitive layer can befurther improved by incorporating a co-sensitizer thereinto. Althoughmechanisms of this improvement are unclear, it is thought that many ofthese are based on the following chemical process. Namely, it ispresumed that a co-sensitizer reacts with various intermediate activespecies (e.g., radicals, peroxides, oxidizing agents, and reducingagents) which have generated as a result of the photoreactions initiatedby light absorption by the photopolymerization initiator (initiatorsystem) described above and during the course of the subsequent additionpolymerization reaction to thereby newly yield active radicals. Suchco-sensitizers can be roughly divided into (a) co-sensitizers which arereduced to generate active radicals, (b) co-sensitizers which areoxidized to generate active radicals, and (c) co-sensitizers which reactwith lowly active radicals to convert them into more active radicals orwhich function as a chain transfer agent. However, with respect to manyof the co-sensitizers, there are no common opinions as to which group ofthese the individual compounds belong to.

(a) Compounds which are Reduced to Generate Active Radical:

Compounds having a carbon-halogen bond: The compounds are thought toundergo reductional cleavage of the carbon-halogen bond to generate anactive radical. Preferred examples thereof includetrihalomethyl-s-triazines and trihalomethyloxadiazoles.

Compounds halving a nitrogen-nitrogen bond: The compounds are thought toundergo reductional cleavage of the nitrogen-nitrogen bond to generatean active radical. Preferred examples thereof includehexaarylbiimidazoles.

Compounds having oxygen-oxygen bond: The compounds are thought toundergo reductional cleavage of the oxygen-oxygen bond to generate anactive radical. Preferred examples thereof include organic peroxides.

Onium compounds: The compounds are thought to undergo reductionalcleavage of a carbon-heteroatom bond or oxygen-nitrogen bond thereof togenerate an active radical. Preferred examples thereof includediaryliodonium salts, triarylsulfonium salts, and N-alkoxypyridinium(-azinium) salts.

Ferrocene and iron-arene complexes: The compounds can reductionallygenerate an active radical.

(b) Compounds which are Oxidized to Generate Active Radical:

Alkylate complexes: The compounds are thought to undergo oxidativecleavage of a carbon-heteroatom bond thereof to generate an activeradical. Preferred examples thereof include triarylalkylborates.

Alkylamine compounds: The compounds are thought to undergo oxidativecleavage of a C—X bond on the carbon atom adjacent to the nitrogen atomto generate an active radical. Preferred examples of X include ahydrogen atom, carboxyl, trimethylsilyl, and benzyl. Examples of thecompounds include ethanolamine and derivatives thereof, N-phenylglycineand derivatives thereof, and N-trimethylsilylmethylaniline andderivatives thereof.

Sulfur-containing compounds and tin-containing compounds: The compoundshaving the same structure as the above-described amine compounds exceptthat the nitrogen atom has been replaced with a sulfur or tin atom cangenerate an active radical by the same mechanism. Furthermore, compoundshaving an S—S bond are also known to sensitize based on S—S-cleavage.

α-Substituted methylcarbonyl compounds: The compounds can undergooxidative cleavage of the bond between the carbonyl and the α-carbon togenerate an active radical. The compounds formed by converting thecarbonyl of these compounds into an oxime ether also function likewise.Examples of such compounds include2-alkyl-1-[4-(alkylthio)phenyl]-2-morpholinopronone-1's and the oximeether compounds obtained by reacting these compounds with ahydroxylamine compound and then etherifying the N—OH.

Sulfinic acid salts: The compounds can reductionally generate an activeradical. Examples thereof include sodium arylsulfinates.

(c) Compounds Which React With A Radical To Convert It Into A HighlyActive Radical or Function As A Chain Transfer Agent:

Compounds having, for example, SH, PH, SiH, or GeH in the molecule areused. These compounds can donate hydrogen to a lowly active radicalspecies to generate a radical, or can be oxidized and then deprived of aproton to generate a radical. Examples thereof include2-mercaptobenzimidazole and derivative thereof.

Many specific examples of those co-sensitizers are given, for example,in Japanese Patent Laid-Open No. 236913/1934 as additives intended toimprove sensitivity. Part of these are shown below. However,co-sensitizers usable in the photosensitive layer in the negativephotosensitive lithographic printing plate of the invention should notbe construed as being limited to these.

Those co-sensitizers also can be subjected to various chemicalmodifications in order to improve the properties of the photosensitivelayer. Examples of usable modification techniques include bonding to aradical-generating part of, e.g., a sensitizing dye, titanocene, oraddition-polymerizable unsaturated compound, incorporation of ahydrophilic group, improvement of compatibility, incorporation of asubstituent for inhibiting crystal precipitation, incorporation of asubstituent for improving adhesion, and conversion into a polymer.

Those co-sensitizers can be used alone or in combination of two or morethereof. The co-sensitizers are used in an amount of generally from 0.05to 100 parts by weight, preferably from 1 to 80 parts by weight, morepreferably from 3 to 50 parts by weight, per 100 parts by weight of thecompound having one or more ethylenically unsaturated double bonds.

[Polymerization Inhibitor]

In forming the photo- or heat-polymerizable negative type photosensitivelayer which is an especially preferred photosensitive layer for use inthe negative photosensitive lithographic printing plate of theinvention, it is desirable to add a small amount of a heatpolymerization inhibitor in order to inhibit the compound having one ormore, polymerizable, ethylenically unsaturated double bonds fromundergoing unnecessary heat polymerization during the production orstorage of a negative type photosensitive composition. Appropriateexamples of the heat polymerization inhibitor include hydroquinone,p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol,benzoquinone, 4,4′-thiobis(3-methyl-6-t-butylphenol),2,2′-methylenebis(4-methyl-6-t-butylphenol), andN-nitrosophenylhydroxylamine cerous salt. The heat polymerizationinhibitor is added in an amount of preferably about from 0.01 to 5% byweight based on the nonvolatile ingredients contained in the wholecomposition. Furthermore, a technique for preventing polymerizationinhibition caused by oxygen may be used according to need whichcomprises adding a higher fatty acid or derivative thereof, such asbehenic acid or behenamide, and causing the compound to be present in ahigher concentration on the surface of the photosensitive layer duringthe drying of the layer after coating. The amount of the higher fattyacid or derivative to be added is preferably about from 0.5 to 10% byweight based on the nonvolatile ingredients contained in the wholecomposition.

[Colorant]

A dye or pigment may be added to the photosensitive layer in thenegative photosensitive lithographic printing plate of the invention forthe purpose of coloring the layer. By the addition of a dye or pigment,the printing plate made from the photosensitive lithographic printingplate can be improved in suitability for plate inspection, such asvisibility and suitability for examination with an image density meter.Pigments are especially preferred colorants because many dyes reduce thesensitivity of the photopolymerizable photosensitive layer. Examples ofthe colorant include pigments such as phthalocyanine pigments, azopigments, carbon black, and titanium oxide and dyes such as EthylViolet, Crystal Violet, azo dyes, anthraquinone dyes, and cyanine dyes.The amount of such dyes and pigments to be added is preferably aboutfrom 0.5 to 5% by weight based on the nonvolatile ingredients containedin the whole composition.

[Other Additives]

Other known additives may be further added in order to improve theproperties of the cured film. Examples thereof include inorganicfillers, plasticizers, and ink receptivity agents capable of improvingthe ink receptivity of the photosensitive-layer surface.

Examples of the plasticizers include dioctyl phthalate, didodecylphthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate,tricresyl phosphate, dioctyl adipate, dibutyl sebacate, andtriacetylglycerol. Such plasticizers may be added in an amount ofgenerally up to 10% by weight based on the sum of the polymeric binderand the addition-polymerizable compound.

For the purpose of improving film strength (press life), which will bedescribed later, an additive such as a UV initiator or heat-crosslinkingagent may be added in order to heighten the effect of heating/exposureafter development.

In a method for forming the photosensitive layer, a photopolymerizablecomposition comprising the ingredients for the photosensitive layer isdissolved in any of various organic solvents and the resultant coatingsolution may be applied to a support or an interlayer which will bedescribed later. Examples of the solvent used here include acetone,methyl ethyl ketone, cyclohexane, ethyl acetate, ethylene dichloride,tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethyleneglycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycolmonomethyl ether, propylene glycol monoethyl ether, acetylacetone,cyclohexanone, diacetone alcohol, ethylene glycol monomethyl etheracetate, ethylene glycol ethyl ether acetate, ethylene glycolmonoisopropyl ether, ethylene glycol monobutyl ether acetate,3-methoxypropanol, methoxymethoxyethanol, diethylene glycol monomethylether, diethylene glycol monoethyl ether, diethyleneglycol dimethylether, diethylene glycol diethyl ether, propylene glycol monomethylether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropylacetate, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone,methyl lactate, and ethyl lactate. These solvents can be used alone oras a mixture of two or more thereof. An appropriate range of the solidconcentration in the coating solution is from 2 to 50% by weight.

The coating amount of the coating solution for forming thephotosensitive layer mainly influences the sensitivity anddevelopability of the photosensitive layer and the strength and presslife of the film obtained through exposure. It is therefore desirable toselect a suitable coating amount according to the intended use of thephotosensitive printing plate. If the coating amount thereof is too low,press life is insufficient. On the other hand, too high coating amountthereof are undesirable in that the photosensitive layer has reducedsensitivity and necessitates much time for exposure and, in addition,the development thereof requires a longer time period. In the case wherethe negative photosensitive lithographic printing plate is one intendedto be subjected to scanning exposure, which is a major purpose of theinvention, the coating amount of the coating solution for forming thephotosensitive layer is preferably about from 0.1 to 10 g/m², morepreferably from 0.5 to 5 g/m², on a dry basis.

[Support]

Known hydrophilic supports for use in negative photosensitivelithographic printing plates can be used without particular limitationsas the support of the negative photosensitive lithographic printingplate of the invention. It is preferred to use a plate-shaped supportwhich is dimensionally stable. Examples thereof include papers, paperslaminated with a plastic (e.g., polyethylene, polypropylene, orpolystyrene), sheets of metals (e.g., aluminum, zinc, and copper), filmsof plastics (e.g., cellulose diacetate, cellulose triacetate, cellulosepropionate, cellulose butyrate, cellulose acetate butyrate, cellulosenitrate, poly(ethylene terephthalate), polyethylene, polystyrene,polypropylene, polycarbonates, and poly(vinyl acetal)s), and papers orplastic films coated with any of those metals by laminating or vapordeposition. A surface of such supports may be subjected to appropriate,known, physical or chemical treatments for the purpose of impartinghydrophilicity, improving strength, etc. according to need.

Especially preferred examples of the support include papers, polyesterfilms, and aluminum sheets. More preferred of these are aluminum sheetsbecause they have satisfactory dimensional stability, are relativelyinexpensive, and can be made to have a surface excellent inhydrophilicity and strength through appropriate surface treatmentsaccording to need. Also preferred is a composite sheet comprising apoly(ethylene terephthalate) film and an aluminum sheet bonded thereto,such as that described in Japanese Patent Publication No. 18327/1973.

The term “aluminum sheet” as used herein means a metallic sheetcomprising aluminum as a major component and having dimensionalstability. The aluminum sheet is selected from sheets of pure aluminum,sheets of an alloy of aluminum as the main component with a small amountof one or more other elements, and plastic films or papers coated withaluminum (or an aluminum alloy) by laminating or vapor deposition.

In the following explanations, the aforementioned supports comprisingaluminum or an aluminum alloy are inclusively referred to as aluminumsupports. Examples of elements other than aluminum which are containedin the aluminum alloy include silicon, iron, manganese, copper,magnesium, chromium, zinc, bismuth, nickel, and titanium. The content ofsuch non-aluminum elements in the alloy is up to 10% by weight. Althougha sheet of pure aluminum is preferred in the invention, an aluminumsheet containing a slight amount of non-aluminum elements may be usedbecause completely pure aluminum is difficult to produce by the currentrefining technology. As described above, the aluminum sheet to be usedin the invention is not limited in composition. It can be suitablyselected from sheets of known aluminum materials in general use such as,e.g., JIS A 1050, JIS A 1100, JISA3103, and JISA3005. The thickness ofthe aluminum support to be used in the invention is about from 0.1 to0.6 mm. This thickness can be suitably varied according to the size ofthe printing machine to be used, the size of the intended printingplate, and the desire of the user. The aluminum support may be suitablysubjected according to need to the surface treatments which will bedescribed below. It may, of course, be used without any surfacetreatment.

[Surface-Roughening Treatment]

Examples of surface-roughening treatments include mechanical surfaceroughening, chemical etching, and electrolytic graining such as thosedisclosed in Japanese Patent Laid-Open No. 28893/1981. Also usable arean electrochemical surface-roughening method in which the aluminumsurface is electrochemically roughened in an electrolytic solution ofhydrochloric acid or nitric acid and mechanical surface-rougheningmethods such as the wire brush graining method in which the aluminumsurface is scratched with a metal wire, the ball graining method inwhich the aluminum surface is sandblasted with abrasive spheres and anabrasive material, and the brush graining method in which the aluminumsurface is roughened with a nylon brush and an abrasive material. Thesesurface-roughening methods may be used alone or in combination of two ormore thereof.

Of those methods, the electrochemical method in which the aluminumsurface is chemically roughened in an electrolytic solution ofhydrochloric acid or nitric acid is useful for surface roughening. Thequantity of electricity applied to the support serving as the anode isin the range of from 50 to 400 C/dm². More specifically, it is preferredto conduct AC and/or DC electrolysis in an electrolytic solutioncontaining 0.1 to 50% hydrochloric acid or nitric acid under theconditions of a temperature of from 20 to 80° C., an electrolysis timeof from 1 second to 30 minutes, and a current density of from 100 to 400C/dm².

The aluminum support which has undergone such a surface-rougheningtreatment may be chemically etched with an acid or alkali. Examples ofetchants suitable for this etching include caustic soda, sodiumcarbonate, sodium aluminate, sodium metasilicate, sodium phosphate,potassium hydroxide, and lithium hydroxide. The preferred ranges ofconcentration and temperature are from 1 to 50% and from 20 to 100° C.,respectively. After the etching, pickling is conducted in order toremove the smut remaining on the surface. Examples of acids which can beused for this pickling include nitric acid, sulfuric acid, phosphoricacid, chromic acid, hydrofluoric acid, and borofluoric acid. Preferredexamples of methods for smut removal especially after theelectrochemical surface-roughening treatment include the method in whichthe support surface is brought into contact with 15 to 65% by weightsulfuric acid at a temperature of from 50 to 90° C. as described inJapanese Patent Laid-Open No. 12739/1978 and the method in which thesupport surface is alkali-etched as described in Japanese PatentPublication No. 28123/1973.

Methods and conditions for the surface-roughening treatment andpost-treatments are not particularly limited as long as the roughenedsurface of the support thus treated has a center-line average surfaceroughness Ra of from 0.2 to 0.5 μm.

[Anodization Treatment]

The aluminum support thus treated, which has an oxide layer formedthereon, is subjected to an an odization treatment. In this anodizationtreatment, an aqueous solution of sulfuric acid, phosphoric acid, oxalicacid, or boric acid/sodium borate or a combination of two or more ofsolutions of these is used as the main component of an electrolyticbath. This electrolytic solution may, of course, contain at least theingredients usually contained in the aluminum alloy sheet, an electrode,tap water, underground water, etc. The electrolytic solution may furthercontain second and third ingredients added thereto. Examples of thesecond and third ingredients include cations such as ions of metals suchas Na, K, Mg, Li, Ca, Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn andammonium ions and anions such as nitrate ions, carbonate ions, chlorineions, phosphate ions, fluorine ions, sulfite ions, titanate ions,silicate ions, and borate ions. The concentration of such ions in theelectrolytic solution may be about from 0 to 10,000 ppm. There are noparticular limitations on the conditions for the anodization treatment.However, the treatment is preferably conducted by DC or AC electrolysisunder the conditions of a concentration of from 30 to 500 g/L, atreating-liquid temperature of from 10 to 70° C., and a current densityof from 0.1 to 40 A/m². The thickness of the film thus formed byanodization is from 0.5 to 1.5 μm, preferably from 0.5 to 1.0 μm.

Conditions for the anodization treatment should be selected so that theanodization film formed on the support thus treated has microporeshaving a diameter of from 5 to 10 nm and a pore density of from 8×10¹⁵to 2×10¹⁶ pores per m².

For hydrophilizing the support surface, various known methods can beused. In an especially preferred treatment, the support surface ishydrophilized with a silicate, polyvinylphosphonic acid, or the like. Afilm is formed in an amount of generally from 2 to 40 mg/m², morepreferably from 4 to 30 mg/m², in terms of silicon or phosphorus amount.

The amount of the film deposited can be determined by fluorescent X-rayspectroscopy.

The hydrophilizing treatment described above can be accomplished byimmersing the aluminum support having an anodization film in an aqueousalkali metal silicate or polyvinylphosphonic acid solution having aconcentration of from 1 to 30% by weight, preferably from 2 to 15% byweight, and a pH at 25° C. of from 10 to 13. The immersion is conducted,for example, at a temperature of from 15 to 80° C. for from 0.5 to 120seconds.

Examples of the alkali metal silicate used in the hydrophilizingtreatment include sodium silicate, potassium silicate, and lithiumsilicate. A hydroxide may be used for heightening the pH of the aqueousalkali metal silicate solution, and examples thereof include sodiumhydroxide, potassium hydroxide, and lithium hydroxide.

A salt of an alkaline earth metal or a salt of a Group IVB metal may beincorporated into the treating liquid. Examples of the salt of analkaline earth metal include water-soluble salts such as nitrates, e.g.,calcium nitrate, strontium nitrate, magnesium nitrate, and bariumnitrate, sulfates, hydrochlorides, phosphates, acetates, oxalates, andborates. Examples of the salt of a Group IVB metal include titaniumtetrachloride, titanium trichloride, titanium potassium fluoride,titanium potassium oxalate, titanium sulfate, titanium tetraiodide,zirconium chloride oxide, zirconium dioxide, zirconium oxychloride, andzirconium tetrachloride.

Such alkaline earth metal salts and Group IVB metal salts can be usedalone or in combination of two or more thereof. The amount of such metalsalts to be added is preferably from 0.01 to 10% by weight, morepreferably from 0.05 to 5.0% by weight.

Silicate electrodeposition such as that described in U.S. Pat. No.3,658,662 is also effective. Furthermore, a surface treatment comprisinga combination of the electrolytic graining disclosed in Japanese PatentPublication No. 27481/1971 or Japanese Patent Laid-Open No. 58602/1977or 30503/1977 with the anodization treatment and hydrophilizingtreatment described above is also effective in preparing a support.

[Interlayer]

An interlayer may be formed in the negative photosensitive lithographicprinting plate of the invention for the purposes of improving adhesionbetween the photosensitive layer and the support and improvingnon-smearing properties. Examples of the interlayer include thosedescribed in Japanese Patent Publication No. 7481/1975, Japanese PatentLaid-Open Nos. 72104/1979, 101651/1984, 149491/1985, 232998/1985,56177/1991, 282637/1992, 16558/1993, 246171/1993, 159983/1995,314937/1995, 202025/1996, 320551/1996, 34104/1997, 236911/1997,269593/1997, 69092/1998, 115931/1998, 161317/1998, 260536/1998,282682/1998, 84674/1999, 69092/1998, 115931/1998, 38635/1999,38629/1999, 282645/1998, 301262/1998, 24277/1999, 109641/1999,319600/1998, 84674/1999, 327152/1999, and 2000-10292, and JapanesePatent Applications Nos. 36377/1999, 165861/1999, 284091/1999, and2000-14697.

[Protective Layer]

In the negative photosensitive lithographic printing plate having aphoto- or heat-polymerizable negative type photosensitive layer, whichis a preferred embodiment of the invention, it is generally preferred toform a protective layer on the photosensitive layer in order to enablethe photosensitive printing plate to be exposed in the air. Theprotective layer prevents the low-molecular compounds such as oxygen andbasic substances present in the air, which inhibit an image-formingreaction induced in the photosensitive layer by exposure, from cominginto the photosensitive layer to thereby enable exposure to be conductedin the air. Consequently, the properties which the protective layer isdesired to have are: low permeability to low-molecular compoundsincluding oxygen; the property of not substantially inhibitingtransmission of the light to be used for exposure; excellent adhesion tothe photosensitive layer; and the ability to be easily removed in adevelopment step after exposure. Various measures in imparting suchproperties to a protective layer have hitherto been taken, and aredescribed in detail in U.S. Pat. No. 3,458,311 and Japanese PatentLaid-Open No. 49729/1980. Preferred examples of materials usable forforming the protective layer include water-soluble polymeric compoundshaving relatively high crystallinity. Specific known examples thereofinclude poly(vinyl alcohol)s, polyvinylpyrrolidone, acid cellulosederivatives, gelatins, gum arabic, and poly(acrylic acid) However, useof a poly(vinyl alcohol), among these polymers, as the main componentgives most satisfactory results with respect to basic propertiesincluding oxygen barrier properties and removability by development. Thepoly(vinyl alcohol) to be used in the protective layer may be one partlysubstituted with an ester, ether, and acetal, as long as it containsunsubstituted vinyl alcohol units, which enable the polymer to have thenecessary oxygen barrier properties and water solubility. For the samereason, a poly(vinyl alcohol) composed of units partly derived from oneor more comonomers may be used. Examples of the poly(vinyl alcohol)include ones which have a degree of hydrolysis of from 71 to 100% and amolecular weight of from 300 to 2,400. Specific examples thereof includePVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS,PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220,PVA-224, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA-420,PVA-613, and L-8, all manufactured by Kuraray Co., Ltd.

Not only oxygen barrier properties and removability by development butalso blurring, adhesion, and marring resistance are taken in account inselecting ingredients for the protective layer (kind of PVA and use ofadditives), the amount of the layer to be formed by coating, etc. Ingeneral, a protective layer containing a PVA with a higher degree ofhydrolysis (a higher content of unsubstituted vinyl alcohol units) andhaving a larger thickness has higher oxygen barrier properties and isadvantageous in sensitivity. However, excessively enhanced oxygenbarrier properties pose problems that an unnecessary polymerizationreaction occurs during production or storage before exposure, and thatimagewise exposure results in unnecessary blurring or line withenlargement. Furthermore, adhesion to the image areas and marringresistance also are extremely important for plate handling.Specifically, when a hydrophilic layer comprising a water-solublepolymer is superposed on the oleophilic photosensitive layer, then thehydrophilic layer is apt to peel off the photosensitive layer due to itsinsufficient adhesive strength and the resultant uncovered parts of thephotosensitive layer cause defects such as curing failures due topolymerization inhibition by oxygen. For improving adhesion between thetwo layers so as to eliminate these problems, various proposals havebeen made. For example, U.S. Pat. Nos. 292,501 and 44,563 describe atechnique for obtaining sufficient adhesion which comprises mixing ahydrophilic polymer consisting mainly of a poly(vinyl alcohol) with from20 to 60% by weight acrylic emulsion, water-insolublevinylpyrrolidone/vinyl acetate copolymer, or the like and superposingthe mixture on a photosensitive layer. Any of such known techniques canbe applied to the protective layer in the invention. Such methods forforming a protective layer by coating are described in detail in, e.g.,U.S. Pat. No. 3,458,311 and Japanese Patent Laid-Open No. 49729/1980.

In a plate-making process for plate-making a lithographic printing platefrom the negative photosensitive lithographic printing plate of theinvention, the plate may be wholly heated according to need before andduring exposure and during the period of from the exposure todevelopment. This heating accelerates an image-forming reaction in thephotosensitive layer to bring about advantages of improved sensitivity,improved press life, and stabilized sensitivity. Furthermore, thetechnique in which the image formed through development is whollysubjected to post-heating or exposure is effective in improving imagearea strength and press life. It is generally preferred that the heatingbefore development be conducted under such mild conditions that theplate is heated at 150° C. or lower. Too high temperatures poseproblems, for example, that the nonimage areas are blurred. Exceedinglysevere conditions are used for the heating after development. Usually,this heating is conducted at a temperature in the range of from 200 to500° C. Too low temperatures are ineffective in sufficiently heighteningthe image area strength, while too high temperatures pose problems ofdeterioration of the support and pyrolysis in the image areas.

For exposing the negative photosensitive lithographic printing plate ofthe invention, known methods can be used without particular limitations.It is desirable to use a light source which emits a light having awavelength of from 300 to 1,200 nm. Preferred examples of the lightsource include various lasers. The mechanism of exposure maybe any ofthe internal drum exposure, external drum exposure, flat bed exposure,and the like. A highly water-soluble ingredient may be used as acomponent of the photosensitive layer in the negative photosensitivelithographic printing plate of the invention, whereby the photosensitivelayer can be made soluble in neutral water and weakly alkaline water. Anegative photosensitive lithographic printing plate having thisconstitution can be used also in such a manner that it is attached to aprinting machine and subjected to exposure and development thereon.

Other examples of the light source for use in exposing the negativephotosensitive lithographic printing plate of the invention includeultrahigh-pressure, high-pressure, medium-pressure, and low-pressuremercury lamps, chemical lamps, carbon arc lamps, xenon lamps, metalhalide lamps, various laser lamps emitting visible or ultraviolet light,fluorescent lamps, tungsten lamps, and sunlight.

The negative photosensitive lithographic printing plate of the inventionis developed after exposure.

An aqueous alkali solution having a pH of 14 or lower is an especiallypreferred developing solution for use in the development. More preferredis an aqueous alkali solution having a pH of from 8 to 12 and containingan anionic surfactant. Examples of the alkali include inorganic alkalissuch as sodium tertiary phosphate, potassium tertiary phosphate,ammonium tertiary phosphate, sodium secondary phosphate, potassiumsecondary phosphate, ammonium secondary phosphate, sodium carbonate,potassium carbonate, ammonium carbonate, sodium hydrogen carbonate,potassium hydrogen carbonate, ammonium hydrogen carbonate, sodiumborate, potassium borate, ammonium borate, sodium hydroxide, ammoniumhydroxide, potassium hydroxide, and lithium hydroxide. Also usable areorganic alkalis such as monomethylamine, dimethylamine, trimethylamine,monoethylamine, diethylamine, triethylamine, monoisopropylamine,diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine,diethanolamine, triethanolamine, monoisopropanolamine,diisopropanolamine, ethyleneimine, ethylenediamine, and pyridine.

Those alkalis may be used alone or in combination of two or morethereof.

An anionic surfactant is preferably added to the developing solution foruse in developing the negative photosensitive lithographic printingplate of the invention in an amount of generally from 1 to 20% byweight, preferably from 3 to 10% by weight. Too small amounts thereofresult in impaired developability, while too large amounts thereofproduce adverse influences such as deterioration in strength, e.g.,wearing resistance, in the image areas.

Examples of the anionic surfactant include sodium lauryl sulfate,ammoniumlauryl sulfate, sodiumoctyl sulfate, salts of alkylarylsulfonicacids, such as sodium isopropylnaphthalenesulfonate, sodiumisobutylnaphthalenesulfonate, the sodium salt of polyoxyethylene glycolmononaphthyl ether sulfate, sodium dodecylbenzenesulfonate, andsodiumm-nitrobenzenesulfonate, sulfuric esters of higher alcohols having8 to 22 carbon atoms, such as disodium alkyl sulfates, phosphoric estersof aliphatic alcohols, such as sodium cetyl phosphate, alkylamidesulfonate salts such as C₁₇H₃₃CON(CH₃)CH₂CH₂SO₃Na, and salts of estersof dibasic aliphatic sulfonic acids, such as sodium dioctylsulfosuccinate and sodium dihexyl sulfosuccinate.

A slightly water-miscible organic solvent, e.g., benzyl alcohol, can beadded to the developing solution according to need. Suitable organicsolvents have a solubility in water of about 10% by weight or lower.Preferably, an appropriate organic solvent is selected from ones havinga solubility in water of 5% by weight or lower. Examples thereof include1-phenylethanol, 2-phenylethanol, 3-phenylpropanol, 1,4-phenylbutanol,2,2-phenylbutanol, 1,2-phenoxyethanol, 2-benzyloxyethanol,o-methoxybenzyl alcohol, m-methoxybenzyl alcohol, p-methoxybenzylalcohol, benzyl alcohol, cyclohexanol, 2-methylcyclohexanol,4-methylcyclohexanol, and 3-methylcyclohexanol. The content of such anorganic solvent is preferably from 1 to 5% by weight based on the totalamount of the developing solution in use. The amount of the organicsolvent to be used is closely related to the amount of the surfactant tobe used. It is preferred to increase the amount of the anionicsurfactant as the amount of the organic solvent increases. This isbecause if a large amount of an organic solvent is added to a developingsolution containing a small amount of an anionic surfactant, the organicsolvent partly remains undissolved, making it impossible to expectsatisfactory developability.

Additives such as an antifoamer and a water softener can be furtheradded according to need. Examples of the water softener includepolyphosphoric acid salts such as Na₂P₂O₇, Na₅P₃O₃, Na₃P₃O₉, Na₂O₄P(NaO₃P) PO₃Na, and Calgon (sodium polymetaphosphate);aminopolycarboxylic acids and derivatives thereof, such asethylenediaminetetraacetic acid and potassium salts and sodium saltsthereof, diethylenetriaminepentaacetic acid and potassium salts andsodium salts thereof, triethylenetetraminehexaacetic acid and potassiumsalts and sodium salts thereof, hydroxyethylethylenediaminetriaceticacid and potassium salts and sodium salts thereof, nitrilotriacetic acidand potassium salts and sodium salts thereof,1,2-diaminocyclohexanetetraacetic acid and potassium salts and sodiumsalts thereof, and 1,3-diamino-2-propanoltetraacetic acid and potassiumsalts and sodium salts thereof; and organic phosphonic acids andderivatives thereof, such as 2-phosphono-1,2,4-butanetricarboxylic acidand potassium salts and sodium salts thereof,2-phosphono-2,3,4-butanetricarboxylic acid and potassium salts andsodium salts thereof, 1-phosphono-1,2,2-ethanetricarboxylic acid andpotassium salts and sodium salts thereof,1-hydroxyethane-1,1-diphosphonic acid and potassium salts and sodiumsalts thereof, and aminotri(methylenephosphonic acid) and potassiumsalts and sodium salts thereof. The optimal amount of such a watersoftener to be added varies depending on the hardness and amount of thehard water used. In general, however, a water softener may beincorporated into the developing solution in use in an amount of from0.01 to 5% by weight, preferably from 0.01 to 0.5% by weight.

In the case where an automatic processor is used in developing thenegative photosensitive lithographic printing plate, the developingsolution fatigues according to the amount of plates processed. In thiscase, the processing ability may be recovered with a replenisher or afresh developing solution. This replenishment is preferably conducted bythe method described in U.S. Pat. No. 4,882,246.

Also preferred are the developing solutions described in Japanese PatentLaid-Open Nos. 26601/1975 and 54341/1983 and Japanese Patent PublicationNos. 39464/1981, 42860/1981, and 7427/1982.

The negative photosensitive lithographic printing plate thus developedis post-treated with washing water, a rinse containing a surfactant andother ingredient, and a desensitizing liquid containing gum arabic, astarch derivative, etc., in the manner described, e.g., in JapanesePatent Laid-Open Nos. 8002/1979, 115045/1980, or 58431/1984. Variouscombinations of these treatments can be used for the post-treatment ofthe negative photosensitive lithographic printing plate of theinvention.

The lithographic printing plate obtained through such treatments ismounted on an offset press and used to print many sheets.

A plate cleaner may be used for removing smudges present on the plateduring printing. As the cleaner is used a known plate cleaner for PSplates. Examples thereof include CL-1, CL-2, CP, CN-4, CN, CG-1, PC-1,SR, and IC (all manufactured by Fuji Photo Film Co., Ltd.).

The invention will be explained below in more detail by reference to thefollowing Examples, but the invention should not be construed as beinglimited thereto.

SYNTHESIS EXAMPLE 1

In 775.0 g of pure water was dissolved 44.7 g of a poly(vinyl alcohol)having a degree of saponification of 99% and a weight-average degree ofpolymerization of 500. This aqueous solution was cooled to 5° C., and1.6 g of concentrated hydrochloric acid (35% by weight) was addedthereto with stirring. Furthermore, 60.6 g of4-(2-acryloyloxyethoxy)benzaldehyde synthesized by the method describedin the Example 1 of International Patent Publication No. 2000-506282 wasadded dropwise to the solution over 10 minutes. Precipitation began at45 minutes after initiation of the dropwise addition. The reactionmixture was heated to 40° C. after 2 hours and then held at thistemperature for 4 hours to obtain poly(vinyl acetal). This poly(vinylacetal) was washed twice with pure water and then neutralized bydispersing the poly(vinyl acetal) into 800 g of pure water andcontinuously stirring the dispersion for 4 hours while keeping the pHthereof at 9.5. The poly(vinyl acetal) thus obtained was dehydrated andthen continuously extracted with n-hexane as a solvent by means of aSoxhlet's extractor over a whole day and night to remove the residualaldehyde. Thus, 101.2 g of poly(vinyl acetal) having acryloyl groups ascrosslinkable groups was obtained. This poly(vinyl acetal) had a degreeof polymerization of 550, and the number of residual hydroxyl groups andresidual acetyl groups contained therein were 44 and 1, respectively.

SYNTHESIS EXAMPLE 2

To 170 g of N,N-dimethylformamide was added 25.3 g of the poly(vinylacetal) obtained in Synthesis Example 1. This mixture was stirred at 50°C. for 3 hours to dissolve the polymer. A solution of 6.1 g of1,2-cyclohexanedicarboxylic anhydride in 30 g of N,N-dimethylformamidewas added dropwise thereto at 50° C. over 15 minutes. Thereafter, 0.6 gof 4-(dimethylamino) pyridine was added thereto and the resultantmixture was stirred at 50° C. for 8 hours and then allowed to cool. Atthe time when the temperature thereof had reached 60° C., 7.3 g ofacetic acid was added. This solution was cooled to room temperature andthen poured into a mixture of 1,400 g of water and 40 g of methanol. Theresultant mixture was stirred for 2 hours. The white solid thusprecipitated was taken out by filtration and dried to thereby obtain30.5 g of the polymer (P-1) shown in Table 1. The weight-averagemolecular weight of this polymer, as measured by gel permeationchromatography and calculated for standard polystyrene, was 67,000. Thenumbers of residual hydroxyl groups and residual acetyl groups containedtherein were 16 and 1, respectively. This polymer had an acid value of1.24 meq/g.

SYNTHESIS EXAMPLE 3

The binder polymers (P-2) to (P-20) and comparative samples (PR-1) to(PR-4) shown in Table 1 were obtained in the same manner.

TABLE 1 Component proportion Molecular Binder Component ComponentComponent Component Component by mole weight Acid value polymer a b c de (a/b/c/d/e) (× 10000) (meq/g) P-1  I-1 III-5 PVA PVAc — 55/28/16/1—6.7 1.24 P-2  I-1 III-7 PVA PVAc — 20/32/29/20/— 4.5 2.25 P-3  I-1 III-3IV-1 PVA PVAc 36/22/21/17/4 9.6 1.10 P-4  I-1  II-4  III-10 PVA PVAc34/9/41/15/1 3.6 1.94 P-5  I-2 III-6 IV-5 PVA PVAc 15/36/40/7/2 5.0 1.56P-6  I-2   I-3 III-5 PVA PVAc 20/25/22/26/7 1.9 0.95 P-7  I-3 III-1 PVAc— — 65/32/3/—/— 2.9 1.02 P-8  I-4 III-9 IV-4 PVA PVAc 26/41/24/8/1 7.41.60 P-9  I-5 III-4 PVA — — 42/25/33/—/— 6.6 1.11 P-10 I-6 III-8 IV-3IV-5 PVAc 35/9/15/26/15 0.8 0.75 P-11 I-7 III-5 IV-6 PVA PVAc35/45/5/10/5 15.8 2.46 P-12 I-8   I-9 III-6 — — 35/35/30/—/— 3.9 0.94P-13 I-8  III-10 PVA PVAc — 9/46/30/15/— 5.2 3.01 P-14 I-9 III-2 PVAPVAc — 45/33/20/2/— 0.9 1.52 P-15 I-9  II-2 III-4 IV-2 PVA 10/30/40/15/55.8 2.01 P-16  I-10 III-1 III-5 PVA PVAc 9/8/43/30/10 4.7 2.77 P-17II-1   III-10 PVA PVAc — 38/34/24/4/— 10.6 2.23 P-18 II-2   II-4 III-2PVA PVAc 20/15/25/38/2 1.5 1.99 P-19 II-3  III-1 III-9 PVA PVAc40/30/10/19/1 12.5 3.35 P-20 II-4  III-5 IV-6 PVA PVAc 42/35/15/7/1 2.61.87 PR-1 III-1   IV-1 PVA PVAc — 33/50/17/5/— 7.2 2.15 PR-2 III-3  IV-2 PVA PVAc — 25/57/8/10/— 4.7 1.66 PR-3 I-1 PVA PVAc — — 55/44/1/—/—3.5 0 PR-4 II-4  IV-6 PVA PVAc — 25/40/30/5/— 6.3 0

EXAMPLES 1 TO 20 AND COMPARATIVE EXAMPLES 1 TO 4

Negative photosensitive lithographic printing plates were produced andevaluated for printing performances in the following manners. Theresults obtained are shown in Table 2.

[Production of Supports]

A JIS A 1050 aluminum sheet having a thickness of 0.24 mm and a width of1030 mm was continuously treated in the following manner.

(a) An existing mechanically surface-roughening apparatus was used tomechanically roughen a surface of the aluminum sheet with rotating nylonbrush rollers while supplying a suspension of an abrasive material(pumice) having a specific gravity of 1.12 in water as an abrasiveslurry to the aluminum sheet surface. The abrasive material had anaverage particle diameter of from 40 to 45 μm and a maximum diameter of200 μm. The nylon brushes were made of nylon-6, 10 and had a bristlelength of 50 mm and a bristle diameter of 0.3 mm. Three rotating brushrollers were used which each comprised a perforated stainless-steelcylinder having a diameter of 300 mm and bundles of such nylon bristlesdensely attached thereto by fitting them into the perforations. Theapparatus had under the brush rollers two supporting rollers (diameter,200 mm) apart from each other at a distance of 300 mm. The brush rollerswere pressed against the aluminum sheet in such a degree that the loadimposed on the driving motor rotating the brush rollers increased to avalue higher by 7 kW than that as measured before the brush rollers werepressed against the aluminum sheet. The direction of rotation of thebrush rollers was the same as the direction of running of the aluminumsheet, and the rotational speed thereof was 200 rpm.

(b) The aluminum sheet was etched by spraying with an etchant solutionhaving a caustic soda concentration of 2.6% by weight and an aluminumion concentration of 6.5% by weight at a temperature of 70° C. todissolve away a surface layer of the aluminum sheet in an amount of 13g/m². Thereafter, the aluminum sheet was washed with water by spraying.

(c) The aluminum sheet was subjected to a de-smutting treatment byspraying with an aqueous solution having a nitric acid concentration of1% by weight (containing 0.5% by weight aluminum ions) and a temperatureof 30° C. Thereafter, the aluminum sheet was washed with water byspraying. The aqueous nitric acid solution used for the de-smutting wasa waste liquid resulting from the step of electrochemical surfaceroughening with an alternating current in an aqueous nitric acidsolution.

(d) A 60 Hz AC voltage was used to continuously conduct anelectrochemical surface-roughening treatment. The electrolytic solutionused was 1% by weight aqueous nitric acid solution (containing 0.5% byweight aluminum ions and 0.007% by weight ammonium ions) having atemperature of 40° C. The AC power source used was one providing atrapezoidal rectangular wave alternating current wherein the TP, whichis the time required for the current value to increase from zero to apeak, was 2 msec and the duty ratio was 1:1. A carbon electrode was usedas a counter electrode to conduct the electrochemical surface-rougheningtreatment using ferrite as an auxiliary anode. The current density was30 A/dm² in terms of peak value, and the quantity of electricity was 255C/cm² in terms of the sum of electricity at the time when the aluminumsheet was functioning as an anode. To the auxiliary anode was supplied5% of the current flowing from the power source. After thissurface-roughening treatment, the aluminum sheet was washed with waterby spraying.

(e) The aluminum sheet was etched by spraying with an etchant solutionhaving a caustic soda concentration of 26% by weight and an aluminum ionconcentration of 6.5% by weight at 32° C. to dissolve away a surfacelayer of the aluminum sheet in an amount of 0.2 g/m². Thus, the smutingredients consisting mainly of aluminum hydroxide yielded by thepreceding step of electrochemical surface roughening with an alternatingcurrent were removed and, simultaneously therewith, the edges of thepits formed were partly dissolved away and rounded. Thereafter, thealuminum sheet was washed with water by spraying.

(f) The aluminum sheet was subjected to a de-smutting treatment byspraying with an aqueous solution having a sulfuric acid concentrationof 25% by weight (containing 0.5% by weight aluminum ions) and atemperature of 60° C. Thereafter, the aluminum sheet was washed withwater by spraying.

(g) An existing anodizing apparatus based on the two-stage-feedelectrolytic processing method (lengths of first and second electrolysiszones, 6 m each; length of first feed zone, 3 m; length of second feedzone, 3 m; lengths of first and second feeder electrodes, 2.4 m each)was used to conduct an anodization treatment under the conditions of asulfuric acid concentration in the electrolysis zones of 170 g/L(containing 0.5% by weight aluminum ions) and a temperature of 38° C.Thereafter, the aluminum sheet was washed with water by spraying. Inthis anodizing apparatus, a current supplied from a power source flowedto a first feeder electrode disposed in the first feed zone and then tothe aluminum sheet through the electrolytic solution to form an oxidefilm on the surface of the aluminum sheet in the first electrolysiszone. The current then passed through an electrolysis electrode disposedin the first feed zone and returned to the power source. On the otherhand, another current supplied from the power source flowed to a secondfeeder electrode disposed in the second feed zone and likewise to thealuminum sheet through the electrolytic solution to form an oxide filmon the surface of the aluminum sheet in the second electrolysis zone.The quantity of electricity fed to the first feed zone from the powersource was equal to that fed to the second feed zone from the powersource. The current density in the surface of the oxide film in thesecond feed zone was about 25 A/dm². In the second feed zone,electricity was fed through the oxide film, which weighed 1.35 g/m². Theamount of the oxide film finally obtained was 2.7 g/m². The aluminumsupport obtained through the steps described above is referred to as[AS-1].

[Hydrophilizing Treatment]

The aluminum support [AS-1] was treated with a silicate in order toenhance hydrophilicity, required of the nonimage areas of a printingplate. In this treatment, the aluminum web was passed through a 1.5%aqueous solution of #3 sodium silicate kept at 70° C., in such a mannerthat the web/solution contact time was 15 seconds. Thereafter, the webwas washed with water. As a result, silicon was deposited in an amountof 10 mg/m². This support is referred to as [AS-2].

[Formation of Interlayer]

A liquid composition (sol) was prepared by the SG method in thefollowing manner. The respective amounts of the following ingredientswere weighed in a breaker. This mixture was stirred at 25° C. for 20minutes.

Tetraethoxysilane 38 g 3-Methacryloxypropyltrimethoxysilane 13 g 85%Aqueous phosphoric acid solution 12 g Ion-exchanged water 15 g Methanol100 g 

The resultant solution was transferred to a three-necked flask. A refluxcondenser was attached thereto, and this three-necked flask was partlyimmersed in a room-temperature oil bath. The temperature of the oil bathwas elevated to 50° C. over 30 minutes while stirring the contents ofthe three-necked flask with a magnetic stirrer. The mixture was allowedto react for further 1 hour while keeping the bath temperature at 50° C.Thus, a liquid composition (sol) was obtained. This sol was diluted witha methanol/ethylene glycol (20/1 by weight) mixture to a concentrationof 0.5% by weight. The dilute sol was applied to the aluminum support[AS-1] with a whirler and the coating was dried at 100° C. for 1 minute.Thus, a coating layer was formed in an amount of 3.5 mg/m². This coatingamount was the amount of silicon element determined by fluorescent X-rayspectroscopy. The support thus produced is referred to as [AS-3].

Subsequently, a liquid having the following composition was applied tothe aluminum support [AS-2] with a wire-wound bar. The coating was driedwith a hot-air drying oven at 90° C. for 30 seconds. The amount of thecoating dried was 10 mg/m².

Copolymer of ethyl methyacrylate and 0.1 g sodium2-acrylamido-2-methyl-1-propanesulfonate (75:15 by mol)2-Aminoethylphosphonic acid 0.1 g Methanol  50 g Ion-exchanged water  50g

The support thus produced is referred to as [AS-4].

A liquid having the following composition was applied to the aluminumsupport [AS-1] with a wire-wound bar. The coating was dried with ahot-air drying oven at 100° C. for 30 seconds. The amount of the coatingdried was 30 mg/m².

Crosslinkable quaternary-ammonium-salt polymer 0.75 g represented by thefollowing formula (weight-average molecular weight determined by GPC,50,000) Methanol  200 g

The support thus produced is referred to as [AS-5].

A liquid having the following composition was applied to the aluminumsupport [AS-1] with a wire-wound bar. The coating was dried with ahot-air drying oven at 100° C. for 30 seconds. The amount of the coatingdried was 10 mg/m².

Phenylphosphonic acid 0.25 g Methanol  200 g

The support thus produced is referred to as [AS-6].

[Formation of Photosensitive Layer]

A negative type photosensitive composition having the following makeupwas applied to each of the aluminum sheets thus treated, in such anamount as to result in the dry coating amount shown in Table 2. Thecoating was dried at 100° C. for 1 minute to form a photosensitivelayer.

(Negative Photosensitive Composition) Addition-polymerizable compound asoptional  1.5 g ingredient (compound shown in Table 2) Binder polymer(compound shown in Table 2)  2.0 g Sensitizing dye (compound shown inTable 2)  0.2 g Photopolymerization initiator (compound shown in  0.4 gTable 2) Co-sensitizing dye (compound shown in Table 2)  0.4 gFluorochemical nonionic surfactant (Megafac F-177, 0.03 g manufacturedby Dainippon Ink & Chemicals Inc.) Heat-polymerization inhibitor 0.01 g(N-nitrosophenylhydroxylamine aluminum salt) Coloring-pigment dispersionhaving the following  2.0 g composition Methyl ethyl ketone 20.0 gPropylene glycol monomethyl ether 20.0 g (Composition ofColoring-Pigment Dispersion) Pigment Blue 15:6 15 pts. wt. Allylmethacrylate/methacrylic acid 10 pts. wt. copolymer (comonomerproportion: 80/20; weight-average molecular weight: 40,000)Cyclohexanone 15 pts. wt. Methoxypropyl acetate 20 pts. wt. Propyleneglycol monomethyl ether 40 pts. wt.

[Formation of Protective Layer]

A 3% by weight aqueous solution of a poly(vinyl alcohol) (degree ofsaponification, 98 mol %; degree of polymerization, 550) was applied tothe photosensitive layer in an amount of 2 g/m² in terms of dry coatingamount. The coating was dried at 100° C. for 2 minutes.

[Exposure of Negative Photosensitive Lithographic Printing Plates]

Using an FD-YAG (532 nm) laser exposure apparatus (plate setterGutenberg, manufactured by Heidelberg), the negative photosensitivelithographic printing plates thus obtained were subjected to solid-imageexposure and dot image exposure, which was conducted under theconditions of 2,540 dpi, 175 lines per inch, and dot percents increasingfrom 1 to 99% by percents, while regulating the exposure power so as toresult in an exposure energy density of 200 μJ/cm² as measured on theplate surface.

[Development/Platemaking]

Into automatic processor FLP-813, manufactured by Fuji Photo Film Co.,Ltd., were introduced the developing solution shown in Table 3 andfinisher FP-2W, manufactured by Fuji Photo Film Co., Ltd. Each platewhich had been exposed was developed under the conditions of adeveloping solution temperature of 30° C. and a developing time of 18seconds. Thus, lithographic printing plates were obtained.

[Image Area Press Life Test]

Printing machine R201, manufactured by Rolland, was used together withGraph G (N), manufactured by Dainippon Ink & Chemicals Inc., as an ink.The solid-image part of each printed matter was examined. The press lifeof the image areas was evaluated in terms of the number of printedsheets obtained by the time when the image began to be blurred. Thelarger the number, the better the press life.

[Forced Dot Area Press Life Test]

Printing machine R201, manufactured by Rolland, was used together withGraph G (N), manufactured by Dainippon Ink & Chemicals Inc., as an ink.At the time when 5,000 sheets had been printed since printinginitiation, the dot areas were wiped with a printing sponge impregnatedwith PS plate cleaner CL-2, manufactured by Fuji Photo Film Co., Ltd.,to remove the ink adherent to the plate surface. Thereafter, 10,000sheets were printed, and the printed matters obtained were visuallyexamined for blind spots in the dot images.

EXAMPLES 21 TO 30 AND COMPARATIVE EXAMPLES 5 TO 7

The negative photosensitive lithographic printing plates shown in Table3 were evaluated for performances in the same manner as in Examples 1 to20.

The compounds given in Tables 2 and 3 are as follows.

[Addition-Polymerizable Compounds]

M-1: Pentaerythritol tetraacrylate (NK Ester A-TMMT, manufactured byShin-Nakamura Chemical Co., Ltd.)

M-2: Glycerol dimethacrylate/hexamethylene diisocyanate urethaneprepolymer (UA101H, manufactured by Kyoeisha Chemical Co., Ltd.)

M-3: Dipentaerythritol acrylate (NK Ester A-9530, manufactured byShin-Nakamura Chemical Co., Ltd.)

[Photopolymerization Initiator Materials in Tables 2 and 3]

[Binder Polymers in Tables 2 and 3]

PA-1:

Allyl methacrylate/methacrylic acid copolymer (comonomer proportion,80/20 by mole)

Acid value determined by NaOH titration, 1.70 meq/g

Weight-average molecular weight determined by GPC, 48,000

PA-2:

Methyl methacrylate/acrylonitrile/N-[(4-sulfamoyl)phenyl]-methacrylamidecopolymer (comonomer proportion, 37/30/33 by mole)

Weight-average molecular weight determined by GPC, 49,000

PA-3:

Polyurethane resin which is a condensation polymer of the followingdiisocyanates and diols

4,4′-Diphenylmethane diisocyanate (MDI)

Hexamethylene diisocyanate (HMDI)

Polypropylene glycol; weight-average molecular weight, 1,000 (PPG1000)

2,2-Bis(hydroxymethyl)propionic acid (DMPA)

Comonomer proportion (MDI/HMDI/PPG1000/DMPA), 40/10/15/35 by mole

Acid value determined by NaOH titration, 1.05 meq/g

Weight-average molecular weight determined by GPC, 45,000

[Developing Solutions]

D-1:

Aqueous solution of pH 10 having the following composition

Monoethanolamine  0.1 pt. wt. Triethanolamine  1.5 pts. wt. Compound ofthe following formula 1  4.0 pts. wt. Compound of the following formula2  2.5 pts. wt. Compound of the following formula 3  0.2 pts. wt. Water91.7 pts. wt.

In formula 1 given above, R¹⁴ represents a hydrogen atom or butyl group.

D-2:

Aqueous solution having the following composition

Potassium hydrogen disilicate  3.0 pts. wt. Potassium hydroxide  1.5pts. wt. Compound of the formula 3 given above  0.2 pts. wt. Water 95.3pts. wt.

TABLE 2 Photosensitive layer Addition- Photo- Dry Press life polymer-polymer- Sensi- coating Develop- Image area izable Binder ization tizingCo- amount ing (× 10000 No. Support compound polymer initiator dyesensitizer (g/m²) solution sheets) Dot area Ex. 1 AS-1 M-1 P-1  I-1 S-1C-1 1.2 D-2 27 excellent Ex. 2 AS-1 M-1 P-2  I-1 S-2 C-1 1.3 D-2 24 goodEx. 3 AS-5 none P-3  I-2 S-1 C-3 1.4 D-2 31 excellent Ex. 4 AS-2 M-3P-4  I-1 S-2 C-1 1.4 D-1 35 good Ex. 5 AS-3 M-2 P-5  I-1 S-2 C-2 1.3 D-235 good Ex. 6 AS-4 none P-6  I-2 S-1 C-3 1.6 D-2 24 excellent Ex. 7 AS-6M-1 P-7  I-1 S-1 C-2 1.2 D-2 23 good Ex. 8 AS-3 none P-8  I-2 S-2 C-11.4 D-2 42 excellent Ex. 9 AS-1 M-2 P-9  I-2 S-1 C-1 1.5 D-2 31excellent Ex. 10 AS-5 M-1 P-10 I-2 S-2 C-2 1.5 D-1 39 excellent Ex. 11AS-3 M-2 P-11 I-1 S-2 C-1 1.4 D-2 25 good Ex. 12 AS-2 none P-12 I-1 S-2C-1 1.3 D-2 24 excellent Ex. 13 AS-1 M-3 P-13 I-2 S-1 C-1 1.4 D-2 30excellent Ex. 14 AS-5 M-3 P-14 I-1 S-2 C-3 1.7 D-1 26 excellent Ex. 15AS-6 M-1 P-15 I-2 S-1 C-1 1.4 D-2 27 good Ex. 16 AS-4 M-2 P-16 I-1 S-2C-1 1.3 D-1 24 excellent Ex. 17 AS-1 none P-17 I-2 S-1 C-1 1.5 D-2 25good Ex. 18 AS-3 M-3 P-18 I-1 S-2 C-3 1.7 D-1 38 excellent Ex. 19 AS-1M-3 P-19 I-1 S-2 C-3 1.5 D-1 30 good Ex. 20 AS-6 M-1 P-20 I-2 S-1 C-11.4 D-2 27 good Comp. Ex. 1 AS-5 M-1 PR-1 I-1 S-1 C-1 1.4 D-2 5 blindspots Comp. Ex. 2 AS-3 M-3 PR-2 I-2 S-2 C-1 1.4 D-2 3 blind spots Comp.Ex. 3 AS-1 M-2 PR-3 I-1 S-1 C-2 1.4 D-2 no image formed Comp. Ex. 4 AS-6M-2 PR-4 I-2 S-2 C-2 1.4 D-2 no image formed

TABLE 3 Photosensitive layer Press life Addition- Photo- Dry Imagepolymer- Weight poly- Sensi- coating Develop- area izable Binder polymerratio merization tizing Co- amount ing (× 10000 No. Support compound 1 2(1:2) initiator dye sensitizer (g/m²) solution sheets) Dot area Ex. 21AS-1 none P-1  P-6  5/5 I-1 S-2 C-1 1.4 D-2 30 good Ex. 22 AS-3 M-3 P-3 P-9  6/4 I-1 S-1 C-1 1.2 D-2 28 good Ex. 23 AS-6 M-2 P-4  P-10 7/3 I-2S-1 C-2 1.2 D-2 34 good Ex. 24 AS-2 M-2 P-9  P-18 8/2 I-1 S-2 C-1 1.4D-1 33 good Ex. 25 AS-3 M-1 P-10 P-11 9/1 I-2 S-2 C-3 1.4 D-1 21excellent Ex. 26 AS-6 none P-17 P-20 3/7 I-2 S-1 C-1 1.6 D-2 24excellent Ex. 27 AS-1 none P-1  PA-1 8/2 I-1 S-1 C-1 1.4 D-2 21excellent Ex. 28 AS-4 M-3 P-1  PA-2 5/5 I-1 S-1 C-1 1.4 D-1 23 excellentEx. 29 AS-3 M-2 P-6  PA-3 7/3 I-2 S-2 C-3 1.7 D-1 22 excellent Ex. 30AS-5 M-1 P-18 PR-3 7/3 I-2 S-2 C-1 1.2 D-1 27 good Comp. Ex. 5 AS-3 M-2PR-1 PR-4 5/5 I-2 S-2 C-1 1.3 D-2 3 blind spots Comp. Ex. 6 AS-2 M-2PR-2 PA-1 8/2 I-1 S-1 C-1 1.5 D-1 1 blind spots Comp. Ex. 7 AS-5 nonePR-3 PA-1 9/1 I-1 S-1 C-3 1.5 D-3 no image formed

EXAMPLES 31 TO 40 AND COMPARATIVE EXAMPLES 8 TO 10

The negative photosensitive lithographic printing plates shown in Table4 were produced. A semiconductor laser having a wavelength of 405 nm wasused as an illuminator to conduct exposure while regulating the exposurepower so as to result in an exposure energy density of 30 μJ/cm² asmeasured on the plate surface. The printing plates obtained wereevaluated for performances in the same manner as in Examples 1 to 30.

TABLE 4 Photosensitive layer Addition- Photo- Dry Press life polymer-polymer- Sensi- coating Develop- Image area izable Binder ization tizingCo- amount ing (× 10000 No. Support compound polymer initiator dyesensitizer (g/m²) solution sheets) Dot area Ex. 31 AS-1 M-1 P-11 I-1 S-3C-1 1.4 D-2 25 good Ex. 32 AS-2 none P-12 I-1 S-3 C-1 1.3 D-2 24excellent Ex. 33 AS-6 M-3 P-13 I-2 S-4 C-2 1.4 D-2 30 excellent Ex. 34AS-3 M-2 P-14 I-1 S-3 C-3 1.7 D-1 26 excellent Ex. 35 AS-6 M-1 P-15 I-2S-4 C-1 1.4 D-2 27 good Ex. 36 AS-4 M-2 P-16 I-1 S-4 C-1 1.3 D-1 24excellent Ex. 37 AS-1 none P-17 I-2 S-3 C-2 1.5 D-2 25 good Ex. 38 AS-3M-3 P-18 I-1 S-3 C-3 1.7 D-1 38 excellent Ex. 39 AS-1 M-2 P-19 I-1 S-4C-3 1.5 D-1 30 good Ex. 40 AS-5 M-1 P-20 I-2 S-3 C-1 1.4 D-2 27 goodComp. Ex. 8 AS-3 M-1 PR-1 I-1 S-4 C-3 1.4 D-2  5 blind spots Comp. Ex.AS-3 M-3 PR-3 I-2 S-3 C-1 1.4 D-1 no image formed 9 Comp. Ex. AS-1 nonePR-4 I-1 S-4 C-2 1.4 D-2 no image formed 10

[Sensitizing Dyes in Table 4]

EXAMPLES 41 TO 60 AND COMPARATIVE EXAMPLES 11 TO 14

[Formation of Photosensitive Layer]

The coating fluid for photosensitive-layer formation shown below wasprepared and applied to the aluminum support [AS-4] with a wire-woundbar in such an amount as to result in the dry coating amount shown inTable 1. The coating was dried with a hot-air drying oven at 115° C. for45 seconds to form a photosensitive layer.

Coating Fluid for Photosensitive-Layer Formation:

Addition-polymerizable compound (compound  1.0 g shown in Table 5)Binder polymer (compound shown in Table 5)  1.0 g Infrared absorber(IR-1) 0.08 g Heat-polymerization initiator (compound shown in  0.3 gTable 5) Fluorochemical nonionic surfactant (Megafac F-176, 0.01 gmanufactured by Dainippon Ink & Chemicals Inc.) Victoria Pure Bluenaphthalenesulfonate 0.04 g Methyl ethyl ketone  9.0 g Propylene glycolmonomethyl ether  8.0 g Methanol 10.0 g

[Formation of Protective Layer]

A 3% by weight aqueous solution of a poly(vinyl alcohol) (degree ofsaponification, 98 mol %; degree of polymerization, 550) was appliedaccording to need to the photosensitive layer in an amount of 2 g/m² interms of dry coating amount. The coating was dried at 100° C. for 2minutes.

[Exposure of Negative Photosensitive Lithographic Printing Plates]

The negative photosensitive lithographic printing plates thus obtainedwere exposed with Trendsetter 3244 VFS, manufactured by Creo andequipped with a water-cooled 40-W infrared semiconductor laser, underthe conditions of an output of 9 W, external-drum rotational speed of210 rpm, plate-surface energy of 100 mJ/cm², and resolution of 2,400dpi.

[Development/Platemaking]

After the exposure, the developing solution shown in Table 5 and asolution obtained by diluting finisher FN-6, manufactured by Fuji PhotoFilm Co., Ltd., with water in a ratio of 1:1 were introduced intoautomatic processor Stabron 900N, manufactured by Fuji Photo Film Co.,Ltd. The plates exposed were developed at 30° C. to obtain lithographicprinting plates.

[Image Area Press Life Test]

Printing machine Lithrone, manufactured by Komori Corp., was usedtogether with Graph G (N), manufactured by Dainippon Ink & ChemicalsInc., as an ink. The solid-image part of each printed matter wasexamined. The press life of the image areas was evaluated in terms ofthe number of printed sheets obtained by the time when the image beganto be blurred. The larger the number, the better the press life.

[Forced Dot Area Press Life Test]

Printing machine Lithrone, manufactured by Komori Corp., was usedtogether with Graph G (N), manufactured by Dainippon Ink & ChemicalsInc., as an ink. At the time when 5,000 sheets had been printed sinceprinting initiation, the dot areas were wiped with a printing spongeimpregnated with PS plate cleaner CL-2, manufactured by Fuji Photo FilmCo., Ltd., to remove the ink adherent to the plate surface. Thereafter,10,000 sheets were printed, and the printed matters obtained werevisually examined for blind spots in the dot images.

TABLE 5 Photosensitive layer Press life Addition- Dry Image polymer-Weight Heat-poly- coating Develop- area izable Binder polymer ratiomerization amount Protective ing (× 10000 No. Support compound 1 2 (1:2)initiator (g/m²) layer solution sheets) Dot area Ex. 41 AS-4 none P-1 none — OI-1 1.4 none D-3 38 excellent Ex. 42 AS-5 M-3 P-2  none — OI-11.2 present D-3 40 good Ex. 43 AS-1 M-2 P-3  none — OI-2 1.2 none D-1 25good Ex. 44 AS-4 M-1 P-5  none — OI-1 1.2 present D-1 33 excellent Ex.45 AS-2 M-3 P-6  none — OI-2 1.3 none D-3 21 excellent Ex. 46 AS-5 M-3P-7  none — OI-3 1.1 none D-3 28 excellent Ex. 47 AS-6 M-2 P-9  none —OI-1 1.3 present D-3 32 excellent Ex. 48 AS-6 M-2 P-10 none — OI-1 1.3none D-2 23 excellent Ex. 49 AS-1 none P-11 none — OI-2 1.3 present D-236 excellent Ex. 50 AS-3 none P-13 none — OI-2 1.5 present D-1 27 goodEx. 51 AS-2 M-3 P-16 none — OI-3 1.2 present D-3 30 good Ex. 52 AS-1 M-3P-18 none — OI-1 1.3 none D-3 24 good Ex. 53 AS-4 M-3 P-20 none — OI-21.4 none D-2 34 good Ex. 54 AS-4 M-2 P-1  P-6  8/2 OI-1 1.2 present D-333 good Ex. 55 AS-5 M-1 P-5  P-16 9/1 OI-3 1.2 none D-1 21 excellent Ex.56 AS-4 M-3 P-17 P-20 8/2 OI-2 1.3 none D-2 24 excellent Ex. 57 AS-4 M-2P-1  PR-1 8/2 OI-2 1.3 none D-1 36 excellent Ex. 58 AS-5 none P-1  PA-15/5 OI-1 1.4 present D-1 23 excellent Ex. 59 AS-3 M-2 P-2  PA-2 7/3 OI-11.1 none D-3 22 excellent Ex. 60 AS-1 M-3 P-5  PR-3 7/3 OI-2 1.3 noneD-2 27 good Comp. AS-1 M-3 PR-1 PR-4 5/5 OI-1 1.3 present D-1 9 good Ex.11 Comp. AS-4 M-2 PR-2 none — OI-1 1.2 present D-3 5 blind spots Ex. 12Comp. AS-5 M-3 PR-3 none — OI-3 1.4 present D-2 no image formed Ex. 13Comp. AS-6 M-3 PR-4 PA-1 9/1 OI-3 1.5 none D-2 no image formed Ex. 14

[Heat-Polymerization Initiators in Table 5]

[Developing Solution in Table 5]

D-3:

Sodium carbonate monohydrate 10 g Potassium hydrogen carbonate 10 gSodium isopropylnaphthalenesulfonate 15 g Sodiumdibutylnaphthalenesulfonate 15 g Sodium salt of ethylene glycolmononaphthyl 10 g ether monosulfate Sodium sulfite  1 g Tetrasodiumethylenediaminetetraacetate 0.1 g  Ion-exchanged water 938.9 g  

Tables 2 to 5 show that printing plates having exceedingly high presslife were obtained from the negative photosensitive lithographicprinting plates having a photosensitive layer containing a modifiedpoly(vinyl alcohol) resin binder according to the invention and a photo-or heat-polymerization initiator.

The negative photosensitive lithographic printing plate of the inventiongives a lithographic printing plate having exceedingly high press lifebecause it has a photosensitive layer containing a modified poly(vinylalcohol) resin binder according to the invention and a photo- orheat-polymerization initiator. The negative photosensitive lithographicprinting plate of the invention is suitable for scanning exposure to alaser beam, is capable of high-speed writing, and further attains highprinting plate productivity.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

What is claimed is:
 1. A negative photosensitive lithographic printingplate comprising a support and a photosensitive layer containing amodified poly(vinyl alcohol) resin binder having a radical-polymerizablegroup and an acid group, and an infrared absorber.
 2. The negativephotosensitive lithographic printing plate as claimed in claim 1,wherein the infrared absorber is a dye or pigment having an absorptionmaximum at a wavelength between 760 and 1200 nm.
 3. The negativephotosensitive lithographic printing plate as claimed in claim 1,wherein the photosensitive layer further contains a heat-decomposableradical generator.
 4. The negative photosensitive Lithographic printingplate as claimed in claim 3, wherein the heat-decomposable radicalgenerator is an onium salt selected from the group consisting of aniodonium slat, diazonium salt and sulfonium salt.
 5. The negativephotosensitive lithographic printing plate as claimed in claim 1,wherein the modified poly(vinyl alcohol) resin binder having aradical-polymerizable group and an acid group contains a repeating unithaving a radical polymerizable group represented by formula (I) and arepeating unit having an acid group represented by formula (III):

wherein A independently represents a radical-polymerizable group, Xrepresents an acid group; R¹ and R³ each independently represents asubstituted or unsubstituted hydrocarbon group having 1 to 30 carbonatoms, and R¹ and R³ each has a valent of (m+1) and (p+1) respectively;and m and p each independently represents an integer of 1 to
 5. 6. Thenegative photosensitive lithographic printing plate as claimed in claim1, wherein the modified poly(vinyl alcohol) resin binder having aradical-polymerizable group and an acid group contains a repeating unithaving a radical-polymerizable group represented by formula (II) and arepeating unit having an acid group represented by formula (III):

wherein B independently represents a radical-polymerizable group, Xrepresents an acid group; R² and R³ each independently represents asubstituted or unsubstituted hydrocarbon group having 1 to 30 carbonatoms, and R² and R³ each has a valent of (n+1) and (p+1) respectively;and n and p each independently represents an integer of 1 to
 5. 7. Thenegative photosensitive lithographic printing plate as claimed in claim6, wherein, in the repeating unit containing a radical-polymerizablegroup represented by formula (II), B as the radical-polymerizable groupis selected from the group consisting of a (meth)acrylamide group, anallyl group, a styrene structure, a vinyl ether structure and anacetylene structure.
 8. The negative photosensitive lithographicprinting plate as claimed in claim 6 wherein the repeating unit having aradical-polymerizable group represented by formula (II) is representedby at least one of formula (II-A) and formula (II-B):

wherein R⁵ represents a hydrogen atom or methyl group.
 9. A method ofplate-making a negative photosensitive lithographic printing plate,which comprises exposing the negative photosensitive lithographicprinting plate as claimed in claim 1 to a laser light of 760 to 1200 nmwavelength, and thereafter developing the exposed plate.
 10. A negativephotosensitive lithographic printing plate comprising a support and aphotosensitive layer which contains: a modified poly(vinyl alcohol)resin binder having a radical-polymerizable group and an acid group; anda photopolymerization initiator, wherein the modified poly(vinylalcohol) resin binder having a radical-polymerizable group and an acidgroup contains a repeating unit having a radical-polymerizable grouprepresented by formula (I) and a repeating unit having an acid grouprepresented by formula (III)

wherein A independently represents a radical-polymerizable group, Xrepresents an acid group; R¹ and R³ each independently represents asubstituted or unsubstituted hydrocarbon group having 1 to 30 carbonatoms, and R¹ and R³ each has a valent of (m+1) and (p+1) respectively;and m and p each independently represents an integer of 1 to
 5. 11. Anegative photosensitive lithographic printing plate comprising a supportand a photosensitive layer which contains: a modified poly(vinylalcohol) resin binder having a radical-polymerizable group and an acidgroup; and a photopolymerization initiator, wherein thephotopolymerization initiator includes a titanocene compound, and themodified poly(vinyl alcohol) resin binder having aradical-polymerization group and an acid group contains a repeating unithaving a radical-polymerizable group represented by formula (II) and arepeating unit having an acid group represented by formula (III)

wherein B independently represents a radical-polymerizable group, Xrepresents an acid group; R² and R³ each independently represents asubstituted or unsubstituted hydrocarbon group having 1 to 30 carbonatoms, and R² and R³ each has a valent of (n+1) and (p+1) respectively;and n and p each independently represents an integer of 1 to
 5. 12. Thenegative photosensitive lithographic printing plate as claimed in claim11 wherein, in the repeating unit containing a radical-polymerizablegroup represented by formula (II), A as the radical-polymerizable groupis selected from the group consisting of a (meth)acrylamide group, anallyl group, a styrene structure, a vinyl ether structure and anacetylene structure.
 13. A method of plate-making a negativephotosensitive lithographic printing plate, which comprises exposing thenegative photosensitive lithographic printing plate as claimed in claim11 to a laser light that has a wavelength longer than 400 nm and shorterthan 760 nm and thereafter developing the exposed plate.
 14. A negativephotosensitive lithographic printing plate comprising a support and aphotosensitive layer which contains: a modified poly(vmyl alcohol) resinbinder having a radical-polymerizable group and an acid group; and aphotopolymerization initiator, wherein the modified poly(vinyl alcohol)resin binder having a radical-polymerizable group and an acid groupincludes a repeating Unit having a radical-polymerizable grouprepresented by at least one of formula (II-A) and formula (II-B) and arepeating unit having an acid group represented by formula (III):

wherein R⁵ represents a hydrogen atom or methyl group, X represents anacid group, R³ represents a substituted or unsubstituted hydrocarbongroup having 1 to 30 carbon atoms, and has a valent of (p+1); and prepresents an integer of 1 to
 5. 15. The negative photosensitivelithographic printing plate as claimed in claim 14, wherein thephotopolymerization initiator is a titanocene compound.
 16. A method ofplate-making a negative photosensitive lithographic printing plate,which comprises exposing the negative photosensitive lithographicprinting plate as claimed in claim 14 to a laser light that has awavelength longer than 400 nm and shorter than 760 nm and thereafterdeveloping the exposed plate.